Building Britain Britain Beneath Your Feet


Building Britain

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This is the Britain we know.

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A patchwork of fields, forests,

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of rugged mountains and dramatic skylines.

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But ours is also a land of secrets

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that you can only see if you look at it in a new way.

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From beneath.

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I'm going to show you Britain as you've never seen it before.

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The hidden world below our cities.

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The engineering genius that powers the nation

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and keeps the country moving.

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I'll be going deeper and deeper underground

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to explore this unknown Britain.

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To experience its awesome wonders.

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The scale and the drama of this place is just off the chart.

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And it's dirtiest surprises.

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I don't even want to know what that is.

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It will change the way you think about our country.

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I want to unlock the secrets of what's above ground

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by understanding what's below.

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How every city, every forest, even every field,

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depends on an extraordinary hidden world beneath our feet.

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'I'm on my way to one of the most

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'amazing structures in modern Britain.'

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I'm about to discover how what goes on below ground

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can have a profound and unexpected impact on what happens above it.

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The realm of the underworld has so often determined

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how Britain's been built over the centuries.

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One building towers over London.

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The tallest ever constructed in Western Europe.

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The Shard.

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London has never, ever looked this good.

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The Shard's over 300 metres tall,

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but until recently, London had precious few skyscrapers.

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It wasn't until the 1960s

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that the first building over 20 storeys went up.

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Now, just compare that to New York. Think about Manhattan,

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where, they've got over 600 skyscrapers

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that were built since the 1890s.

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Now, what is the difference?

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# One, two, get down. #

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It's all to do with what's underground.

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You might assume you're best to build on something solid,

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and you'd be absolutely right.

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New York sits on hard rock.

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This makes it relatively easy to secure skyscrapers into the ground

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and support their colossal weight.

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Classic skyscrapers, like the Chrysler Building,

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built as early as 1930.

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And the Empire State Building a year later.

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Then the tallest building in the world.

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So, why doesn't London have a skyline like Manhattan's?

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Well, it's all to do with what's underground.

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Last time I did this was in about 1983.

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-Right, I'm going to step back.

-I'd stand well back if I were you.

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'Underneath most of London is this stuff.

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'Soft, squidgy clay.

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'A huge challenge for Roma Agrawal,

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'a structural engineer who helped design The Shard.'

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This is London clay, straight out of the ground.

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This is the stuff that you would actually build on.

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But is it the same clay that you'd get in your modelling shops

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to make a pot, or a mug, or something?

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Amazingly, the answer is yes.

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All these pots and things that we make out of clay

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and the stuff that we're putting our buildings on top of in London

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are pretty much the same thing.

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Let me get an idea, how difficult is it to actually build in London,

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compared with somewhere like New York,

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which is pretty much building straight onto bedrock?

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Yeah, exactly. So New York is actually brilliant for skyscrapers.

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You come in, you put the skyscraper on the rock

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and the rock is very strong.

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And the loads just go straight down into it.

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In London, we need to do a bit more kind of gymnastics around the soil

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to try and make sure that our loads are going down where it should be.

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It's bizarre that this is the exact material

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that you're building huge skyscrapers on.

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It is very difficult to believe.

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Yeah. It just seems... Why would you?

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Well, we don't have a choice, do we, in London?

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'Building on soft ground can have catastrophic consequences.'

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In 2009 in Shanghai, China,

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a 13-storey building was being constructed.

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Its foundations couldn't support its weight.

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And one day, it simply toppled over.

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Despite the devastation, only one worker died.

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'So, just how do you build the tallest building in Britain

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'on soft, unstable clay?

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'Well, to answer that, we're going to reveal how it would look

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'from an entirely different angle.

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'From beneath the ground.'

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Imagine the earth is made of glass

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and you could look up and see the street level above.

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From down here, we can see a completely new subterranean world.

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Tube trains thunder below the surface,

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carrying millions of us to work each day.

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And next to London Bridge Station, the base of The Shard,

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sitting on the soft, unstable clay.

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The Shard needs foundations,

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and not just any old foundations.

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18,000 tonnes of building is kept upright

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by over 100 concrete piles.

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And they're deep.

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Most foundations only go down a few metres.

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The Empire State Building's are just 16 metres deep.

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But The Shard's are three times deeper.

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An astonishing 53 metres down.

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Deeper than Nelson's Column is tall.

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So building London's new skyline has required

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some of the most impressive foundations in the world.

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Its 53-metre-deep foundations mean that The Shard remains,

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and will remain, firmly rooted to the spot.

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And thanks to these new techniques in digging ultra-deep foundations,

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it means that London has had a real growth spurt in recent years.

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We've seen all these new skyscrapers popping up all over the place.

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You've got the Cheesegrater building

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and you've got the Walkie-Talkie building and The Gherkin.

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Who would have thought that that soft London clay

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would have such a profound effect on the London skyline?

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This may be one of the great sights of modern Britain,

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yet the real wonder is the secret world that lies beneath.

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Across the country, it's often the natural landscapes

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that dominate our view.

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Forests and fields, rolling hills,

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ancient mountains.

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But some of our most spectacular wonders are invisible,

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hidden underground.

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This is Gaping Gill in North Yorkshire.

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A hole in the ground that swallows a river.

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People once believed this was a gateway to hell.

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More people have summated Everest than have abseiled into Gaping Gill,

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and I can understand why.

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When you look over the edge, it's just a black void into nothingness.

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And that stream that you can see going over the edge

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that doesn't look too dramatic,

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it actually turns into a waterfall twice the height of Niagara Falls.

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There is only one way, really, to explore it,

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and that's to go over the edge.

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I hope this looks nice from where you're sitting

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because from where I am, it is bloody terrifying.

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Ah! My God, just look at it!

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The scale and the drama of this place is just off the chart.

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It's much bigger and more impressive than I could imagine.

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'With a vertical drop of over 100 metres,

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'this is the tallest waterfall in Britain.

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'A hidden natural wonder.

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'And standing here, you can feel its raw, elemental power.'

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And that water that pours down, it's not just here for dramatic effect.

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That water is a real force of nature.

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It's carved out Gaping Gill.

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We think of the ground as pretty solid,

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but down here, water has created a void as vast as York Minster.

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So, just why did this gigantic underground cathedral

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form in this particular place?

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'Well, the water isn't quite what it seems.'

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I've got some acid and a little pipette.

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And if I put a little bit on the limestone,

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you should see it fizz away

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as it starts to dissolve the limestone. Let's have a go.

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That's the one. Yeah, there you go. You can start to see it fizz away

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as it eats away the limestone.

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That's what's happening in here, but very, very slowly.

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'The water that pours down here is, in fact, a weak acid.

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'It forms when rainwater mixes with carbon dioxide in the air and soil

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'to make carbonic acid.

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'The same stuff that's in fizzy drinks.

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'And that acid reacts with the particular type of rock

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'that exists here. Limestone.'

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It's this process, drawn out over 30 million years,

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that's carved out Gaping Gill.

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Hidden beneath these limestone hills.

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'To escape the cavern, I've had to crawl for over a kilometre

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'through a labyrinth of narrow passages.'

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What's this? Oy-oy-oy!

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From Britain's biggest underground cavern...to the smallest.

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See, getting down was the easy bit.

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Getting up is...is really difficult!

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As I emerge from the womb,

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I feel like I'm being born again.

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That was one of the hardest day's filming ever.

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It's really interesting because just in terms of fear factor,

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you have that terrible fear of heights

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combined with dreadful claustrophobia.

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On every level, it was dreadful!

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Across Britain, there are many more vast cave systems.

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One stretches 90 kilometres,

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nearly twice as long as the Channel Tunnel,

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linking Cumbria, Lancashire and Yorkshire.

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In fact, wherever you find limestone like that at Gaping Gill,

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chances are there's a hidden network of caves and rivers below.

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But if you live in a city, you might be just as surprised

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at the extraordinary things you'd find beneath your streets.

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Nowhere is this more true than Bristol.

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You just need to know where to look.

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I'm on my way to a place few people ever go, or even know about.

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'This is the River Frome.

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'And I'm about to pass into a lost world

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'hidden below the city of Bristol.'

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Here we go.

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'Down here, the river's been entirely covered over,

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'made invisible to the world above.

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'My guide on this unique journey is explorer, Dave Talbot.'

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I've a feeling we are well and truly off the Bristol tourist trail now.

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We certainly are, yeah.

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Over the last 200 years, this river's been

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sort of built and covered over more and more.

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-The last section was done in 1930.

-Yeah.

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And since then, very few people have been down here.

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'As the city expanded, the River Frome got in the way.

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'So it was simply built over. Creating this secret world.'

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It's quite odd. You've got a lovely river that comes through Bristol,

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it's very picturesque, and then suddenly, they just decide,

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"Oh, we'll just cover it over now!"

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'Without building over The Frome,

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'many of the roads, houses and shopping centres

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'of modern Bristol couldn't have existed.

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'A mile in and we're passing under the main shopping streets.

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'And no-one knows we're below them.'

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Every so often, you can hear cars above us.

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Yeah, you can. It's quite eerie, isn't it,

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to think that you're underneath the road.

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'Another half mile or so, the tunnel begins to get lower

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'as we pass under the very heart of Bristol.'

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Actually, the thing that strikes me when you come down here is that

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it really is a case of human needs versus nature.

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So over the last couple of hundred years, obviously,

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Bristol became very successful and expanded.

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And as a result, the whole river has had to be completely confined

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and hidden away from view.

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'A bit further, and the headroom's even tighter.

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'To be honest, I'm getting a bit nervous down here.

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'But finally, after a treacherous six-hour journey,

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'we emerge in Bristol harbour.'

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Did you remember the key, Dallas?

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There we are. Escape from The River Frome.

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'Who'd have thought you could canoe under Bristol

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'through a hidden underworld that most people don't know exists?

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'And across Britain, millions of us

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'go about our daily lives above lost rivers.'

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There's the River Sheaf of Sheffield.

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The River Farset of Belfast.

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The River Sherbourne of Coventry.

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And in London, you might think of The Thames as the only river,

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but there's another hidden underground

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that's transformed the city above.

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The River Fleet.

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'The only visible signs above that this river still exists

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'is the street that bears its name.

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'But The Fleet has been put to work.

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'It performs a role so vital that without it,

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'London could not be the city it is now.'

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I've got to say, actually, looking down here,

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it doesn't look like much of a river at all.

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There's just a short ladder going down.

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But if you want to explore the River Fleet these days,

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you have to go underground.

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'I'm entering a world that's not for the faint-hearted,

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'or the weak-stomached.'

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Here we are, this is the River Fleet.

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It looks like a sewer, smells like a sewer.

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Whoo!

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'That's because it is a sewer.

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'Back in the early 19th century, the open River Fleet

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'was essentially a cesspit carrying disease through London.

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'So it was decided to cover it up.

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'And using 318 million bricks,

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'Victorian engineers turned it into this.

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'It means that millions of us can now live

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'without the risk of disease in a few square miles.

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'But it also hides some pretty gruesome surprises.

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'Dave Dennis is one of an army of underground workers

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'that keep The Fleet flowing.

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'Surely, one of the least-enviable jobs in Britain.'

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So this is the main sewer tunnel.

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Are there tributary sewer tunnels that come off it, or is this it?

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Yeah. Yeah, there's loads.

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Obviously, down very small side roads, you get a main sewer,

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and they drop into a trunk sewer, which we're standing in.

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And if you look over here, there's a small junction,

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which basically is a small sewer.

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What comes out of here, this is human waste?

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Straight from the toilet, that is. Direct from the toilet.

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-Man!

-Direct from the customer.

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-Oh, the smell!

-Yeah, I know.

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DALLAS COUGHS

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Oh, man!

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'Every underground labyrinth has its monster, as I'm about to discover.

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'Down here, it's not a minotaur,

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'it's something far, far worse.'

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Oh, God!

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Oh, the stink!

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Oh, my God, that is horrendous!

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Is this white stuff just fat?

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This is pure fat that's solidified with other material.

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This has come from all over London

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-and it congeals here because it's a bit of a bottleneck.

-Right.

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You have to come and break it up?

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-We have to come down and break it up for it to flow downstream.

-OK.

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'Down here lives the fatberg.

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'A mixture of rancid fat,

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'human excrement and other unmentionables.'

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Oh, Christ!

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You all right?

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DAVE CHUCKLES

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Do you want to get out, Dallas?

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Oh, God, the smell!

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-Look at the size of that!

-This is a...

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-So, this is...this is a fatberg?

-This is a fatberg.

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-Look at the size of it!

-See the worms in it?

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It's got worms in it?!

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-Oh!

-DALLAS COUGHS

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'Nothing could have prepared me for the overpowering smell.'

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DALLAS COUGHS AND GAGS

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You all right there?

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What did you have for breakfast(?) DAVE LAUGHS

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Yeah, might see it.

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This is one big berg.

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Where does that rate on the berg scale?

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-That's a...

-Is that a big one?

-Pretty good one.

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Oop! It's breaking up quite nicely, though.

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Shall I give it a...?

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Yeah, give it a...give it a go.

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This is worm heaven.

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-So...

-What the hell is that?

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-God knows!

-I don't even know what that is.

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This is the most disgusting thing

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I've ever done in my life, without a shadow of a doubt.

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The worst thing is, yeah,

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getting a bit of splashback and getting it in your mouth.

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DAVE CHUCKLES

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So when you guys say, actually,

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please don't pour fat down your sink, you actually mean...

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-Bin it, don't cook it.

-..can you really not pour fat down your sink?

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'What begins as an innocent bit of grease in your kitchen

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'can quickly transform into the monster fatberg.

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'This is a job I don't want to repeat any time soon.

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'London's clean, fresh air has never smelt so good.'

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It is only because of sophisticated sewer systems like we have in London

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that millions of us can live together hygienically

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and safely, well, relatively, anyway.

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But, cities wouldn't work without all that underground

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engineering and infrastructure.

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Places like London and Glasgow

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and Newcastle and Manchester just wouldn't exist.

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'But there's more beneath our cities than the worlds we've built.

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'If we go deeper, we can discover an older, more spectacular kingdom.

0:22:560:23:02

'One that shaped the lives of millions of us.'

0:23:020:23:04

Bath. One of Britain's most genteel cities,

0:23:090:23:13

and perhaps our most famous spa town.

0:23:130:23:16

Where, for centuries,

0:23:160:23:18

people have come to indulge themselves in the waters.

0:23:180:23:21

Yet you might never guess that beneath the city

0:23:210:23:23

is a trap door into a dramatic underworld.

0:23:230:23:26

'But that story starts out in the countryside.'

0:23:280:23:30

To understand how the city of Bath came to be,

0:23:350:23:38

you need to come up here, into the Mendip Hills.

0:23:380:23:41

Now, this is a pretty ordinary stream.

0:23:410:23:43

And it's only about 15 miles to Bath

0:23:430:23:46

from where I'm standing here, as the crow flies.

0:23:460:23:49

But this water is about to go on an extraordinary journey.

0:23:490:23:53

A journey that's going to take around about 10,000 years.

0:23:530:23:57

Soon, the stream plummets down a hole.

0:23:590:24:02

From here, the water travels deeper and deeper into the earth.

0:24:070:24:11

To follow its tortuous underground route,

0:24:130:24:16

surprisingly enough, I need to take to the air.

0:24:160:24:19

So I've hitched a ride with my new friend, Julian, in his plane

0:24:220:24:26

so we can follow the journey, albeit in much quicker time.

0:24:260:24:29

So behind me that way, you've got the Mendip Hills, where we were.

0:24:290:24:33

And straight ahead of me, it's only 15 miles or so, is the city of Bath.

0:24:330:24:37

Now what's going on is down to some very, very,

0:24:370:24:39

interesting geology beneath our feet.

0:24:390:24:42

'From up here, the landscape looks the picture of Middle England.

0:24:440:24:48

'But below the surface is a world closer

0:24:480:24:51

'to the furnace of volcanic Iceland.'

0:24:510:24:53

The water cascades down cracks in the rock,

0:24:570:24:59

pulled deeper towards the centre of the Earth.

0:24:590:25:03

It gets hotter the deeper it goes.

0:25:030:25:06

Until nearly two miles down, it's forced back up towards the surface.

0:25:060:25:10

A vast, natural steam engine hidden deep below ground.

0:25:120:25:16

And here we are over the city of Bath.

0:25:220:25:24

And this is where the water reappears 10,000 years later or so.

0:25:240:25:30

We've done it in, what, five minutes?

0:25:300:25:32

10,000 years!

0:25:320:25:34

It seems like an incredibly long time.

0:25:340:25:37

If you think about the Pyramids, for example, that's 4,000 years ago,

0:25:370:25:40

so 10,000 years, the rains in the Mendip Hills

0:25:400:25:43

have taken to get to Bath.

0:25:430:25:45

'This is where the water finally emerges.'

0:25:560:25:59

And if you look, just on the surface of the water,

0:26:050:26:08

you can see little bubbles where you can see it percolating through.

0:26:080:26:11

You can feel the heat against your face.

0:26:110:26:14

And the funny thing is, it's not the buildings themselves

0:26:140:26:18

that are the oldest thing here, it's actually the water.

0:26:180:26:21

Apparently, it's very medicinal.

0:26:210:26:23

Mm!

0:26:260:26:27

Really metallic.

0:26:270:26:29

I can taste that iron kind of taste.

0:26:290:26:31

I'm going to put that to one side, I think.

0:26:310:26:33

'When the Ancient Romans first arrived in Britain,

0:26:370:26:40

'the hot water bubbling up from the ground

0:26:400:26:42

'appealed to their fondness for bathing.

0:26:420:26:46

'And 2,000 years ago,

0:26:460:26:47

'they founded a city around these hot springs.

0:26:470:26:50

'Today, both city and springs are still thriving.

0:26:510:26:55

'And now I'm taking my first plunge into 10,000-year-old hot water.'

0:26:550:26:59

Seems quite decadent, doesn't it?

0:27:100:27:12

The idea of an open-air heated swimming pool in Britain.

0:27:120:27:16

But you've got to remember that the water in this pool

0:27:160:27:19

is all heated naturally inside the earth.

0:27:190:27:21

It gets to about 60 degrees.

0:27:210:27:23

And then when it comes up out of the ground, it's about 46 degrees,

0:27:230:27:27

and then here, they cool it to a nice balmy 33 degrees,

0:27:270:27:31

which is the ideal temperature for my morning constitutional.

0:27:310:27:36

But because of that high heat that occurs inside the Earth,

0:27:360:27:39

this is Britain's only true hot spring.

0:27:390:27:42

'This modern spa is a continuation of what the Romans began.'

0:27:450:27:49

I think the really interesting thing about Bath,

0:27:510:27:55

and it is the most beautiful city,

0:27:550:27:57

is that it is only here because of the geology.

0:27:570:28:00

'Bath may be the hottest spring in Britain,

0:28:030:28:05

'but there are others dotted around the country.'

0:28:050:28:08

So the fashion for taking the waters

0:28:090:28:12

led to a proliferation of many other spa towns.

0:28:120:28:15

But one city more than any other

0:28:160:28:18

has been shaped by even more ancient and violent forces.

0:28:180:28:22

Edinburgh. A beautiful city that's grown up around this.

0:28:250:28:29

The magnificent castle.

0:28:300:28:31

It dominates the skyline.

0:28:330:28:34

Up here, you can instantly see why this is the perfect place to put your castle.

0:28:400:28:44

We're nice and high, we've got very, very steep banks

0:28:440:28:47

and you can see for miles and miles and miles.

0:28:470:28:50

It's the perfect place to put a stronghold.

0:28:500:28:52

But there's something curious about the rock the castle stands on.

0:28:550:28:59

On three sides, the rock is a sheer face,

0:29:010:29:03

but on the fourth side, a ridge of land slopes gently downwards.

0:29:030:29:08

Seen from beneath, we can follow its course.

0:29:120:29:15

Over centuries, the city was built on this slope,

0:29:180:29:22

becoming the central spine of Edinburgh's Old Town,

0:29:220:29:25

the Royal Mile.

0:29:250:29:26

And at its head, the great rock where the castle stands above.

0:29:280:29:32

This is the gateway to an ancient and violent underworld

0:29:350:29:39

that holds the secret of Edinburgh itself.

0:29:390:29:41

350 million years ago,

0:29:470:29:50

what's now Edinburgh was sitting on a violent volcano.

0:29:500:29:53

Liquid magma surged upwards from beneath the earth.

0:29:550:30:00

Once it stopped, the magma that had made its way to the surface

0:30:000:30:03

cooled and formed solid rock.

0:30:030:30:06

This is called basalt, and it's one of the hardest rocks on earth.

0:30:100:30:13

And it's actually solidified lava.

0:30:130:30:16

So all of this would have been molten.

0:30:160:30:18

And if you look, you can see there's all these cracks. There's one here.

0:30:180:30:23

So this liquid rock would have cooled and contracted,

0:30:230:30:26

which is how you get these cracks.

0:30:260:30:28

'Castle Rock is all we can now see of the violent volcanic forces

0:30:310:30:35

'that shaped this city.'

0:30:350:30:37

The tip of a gigantic pillar of basalt

0:30:400:30:42

that stretches hundreds of metres down into the earth.

0:30:420:30:45

But that's not the end of Edinburgh's story.

0:30:480:30:50

During the Ice Ages, glaciers moved across the land.

0:30:520:30:57

They gouged out the softer rock around the hard, ancient volcano,

0:30:590:31:04

leaving just the Castle Rock

0:31:040:31:06

and a protected sloping ridge in its shadow.

0:31:060:31:09

Standing here, you can see all the evidence of this powerful

0:31:120:31:14

and ancient geological activity.

0:31:140:31:16

So you've got the Castle Rock itself, this volcanic plug

0:31:160:31:20

of very, very hard basalt that would have stood firm

0:31:200:31:23

in the face of the oncoming glacier.

0:31:230:31:25

And then behind it, you've got this tail of sloping ground

0:31:250:31:29

that would have survived where the Old Town is built.

0:31:290:31:34

'So if you're on the castle ramparts,

0:31:350:31:37

'you're standing on top of an ancient volcano.'

0:31:370:31:40

Sometimes, the rocks beneath us have made us rich.

0:31:460:31:49

We may not have diamonds hidden underground in Britain,

0:31:510:31:55

but we've something that's turned out to be far more valuable.

0:31:550:31:58

Coal.

0:32:040:32:06

Coal was the beating heart of the Industrial Revolution.

0:32:060:32:10

It drove the wheels of commerce and fired the factories.

0:32:100:32:14

It turned Britain into an industrial superpower

0:32:140:32:17

and helped grow the Empire.

0:32:170:32:19

Coal put the great into Britain.

0:32:210:32:23

And the best way to get it was deep underground.

0:32:240:32:27

For most of us, it's a world we can barely imagine.

0:32:280:32:32

An underground very few of us experience.

0:32:320:32:34

But in its heyday, mining was Britain's most important industry.

0:32:360:32:40

And for these miners, this wasn't Britain beneath their feet,

0:32:410:32:44

this WAS their Britain.

0:32:440:32:46

'I've come to West Yorkshire to one of the few collieries

0:32:490:32:53

'where you can still descend to a coalface.'

0:32:530:32:55

-How deep are we going to go now?

-140 metres underground.

0:32:570:32:59

-It's going to take approximately...

-That's pretty deep!

0:32:590:33:02

Collieries were much, much deeper than that.

0:33:020:33:04

You look at some of the Yorkshire coalmines, they were as deep as 1,000 metres.

0:33:040:33:07

So relatively, it's a relatively shallow coalmine.

0:33:070:33:10

'It certainly seems deep enough for me.

0:33:140:33:16

'Very few of us go this deep underground these days,

0:33:170:33:20

'but at its peak this was the daily commute to work

0:33:200:33:24

'for vast armies of miners.'

0:33:240:33:26

This way, Dallas.

0:33:310:33:33

'The riches that drew them down here

0:33:360:33:39

'had lain secretly buried for millions of years.'

0:33:390:33:43

I've got a lovely fossil here

0:33:430:33:44

of a tree fern that's come from a coalface.

0:33:440:33:47

You can make out the shape of the bark here.

0:33:470:33:50

And it's really good evidence of where coal actually comes from.

0:33:500:33:53

So trees would have died, they would have rotted down,

0:33:530:33:56

they would have become compressed.

0:33:560:33:58

Eventually becoming peat and then coal.

0:33:580:34:02

And it's funny to think that the only reason we have coal in Britain,

0:34:020:34:06

so much of it, is because 300 million years ago,

0:34:060:34:10

the entire country would have been covered in swampy forests.

0:34:100:34:13

And this is the result.

0:34:160:34:17

An underground world where miners spent their entire working lives.

0:34:170:34:22

This is just one tunnel, but if we could see through the earth,

0:34:220:34:26

then we could reveal the entire mine network.

0:34:260:34:29

This mine complex has a central shaft

0:34:300:34:33

that descends 140 metres into the Earth.

0:34:330:34:35

Branching off the main shaft are four galleries.

0:34:360:34:39

Each one tapping into a coal seam.

0:34:390:34:42

Along each working seam, a branching, intricate network

0:34:440:34:47

of many smaller tunnels spreads out into the coal.

0:34:470:34:51

There'd be teams of miners working on each coalface.

0:34:520:34:55

'Steve Guest is giving me a tiny insight

0:34:590:35:01

'into what life down here was like for the miners.'

0:35:010:35:04

The technique you're going to be using, Dallas,

0:35:060:35:08

down, pick low, undercut it

0:35:080:35:12

-and drop it down onto the floor.

-OK, let's have a go.

0:35:120:35:15

-So, if I sort of go in here, around about here?

-Yeah, that's right.

0:35:150:35:18

So we're chipping away at the bottom,

0:35:230:35:25

the idea that the coal seam above us would have fallen down,

0:35:250:35:28

but presumably, that would have also been very, very dangerous, as well.

0:35:280:35:31

Very, very dangerous. It's not only the coal seam that come down.

0:35:310:35:34

If you've got weak rock above, this is going to collapse on top of you.

0:35:340:35:38

Lots of fatalities on a daily basis.

0:35:380:35:41

This is how the industry was.

0:35:410:35:42

I'm trying to imagine what it would've been like

0:35:450:35:47

with dozens of miners in this cramped area.

0:35:470:35:49

Small conditions, yeah. All working together.

0:35:490:35:52

But this is what their daily work would be.

0:35:520:35:54

Man, it's frustrating! I just want to take a big swing and I can't!

0:35:580:36:01

-That's me done!

-You don't think you'd have had a career in mining?

0:36:070:36:11

Well...I'd like to say yeah,

0:36:110:36:14

but if I'm honest, I think I would have, er...

0:36:140:36:16

I think I would have struggled with this.

0:36:160:36:19

'In this mine alone, there were 240 miners working underground.

0:36:210:36:26

'In total, a staggering 1.25 million people

0:36:260:36:30

'once worked down mines like this.

0:36:300:36:32

'That's as many people who today live in Sheffield, Newcastle

0:36:320:36:36

'and Manchester combined.'

0:36:360:36:38

Across Britain, in the coalfields that lay under Yorkshire

0:36:410:36:44

and Lancashire, the Midlands and the North-East,

0:36:440:36:47

under South Wales and lowland Scotland,

0:36:470:36:50

there were over 3,000 mines.

0:36:500:36:53

And above ground, major cities grew on the back of coal

0:36:530:36:57

and the industry it fuelled.

0:36:570:36:59

The riches below defined much of the urban map of Britain

0:37:000:37:04

responsible for where millions of us live today.

0:37:040:37:07

Mining may be fading from our lives,

0:37:120:37:14

but as so often in our islands,

0:37:140:37:17

what's left can be put to eccentric use.

0:37:170:37:20

As time marches on, our needs and our priorities shift.

0:37:210:37:26

And here in the Lake District is a really good example of that.

0:37:260:37:29

'Under a mountain, a slate mine has been appropriated

0:37:320:37:35

'for a rather different purpose.

0:37:350:37:37

'With their usual pitch destroyed by flooding,

0:37:390:37:41

'the Threlkeld Cricket Club

0:37:410:37:44

'has been forced to some rather unusual measures

0:37:440:37:46

'to raise funds for the repairs.

0:37:460:37:49

'Extreme cricket.'

0:37:490:37:51

CHEERING AND APPLAUSE

0:37:570:38:00

I'm better in daylight.

0:38:000:38:02

I've always been bad at cricket

0:38:020:38:04

and I'm even worse playing it in a slate mine.

0:38:040:38:06

'However with such a small pitch size,

0:38:060:38:09

'even I should manage a four, or even a six.

0:38:090:38:12

'Surely I can hit something!'

0:38:140:38:16

MUSIC: Soul Limbo by Booker T & The MGs

0:38:160:38:20

Quick single! Yes!

0:38:260:38:28

CHEERING

0:38:380:38:40

'A very disappointing innings.

0:38:400:38:42

'And sad to say, my efforts are more Fred Flintstone

0:38:440:38:47

'than Freddie Flintoff.'

0:38:470:38:48

Some 97% of the land area of Britain is countryside.

0:39:000:39:04

It dominates the map.

0:39:050:39:07

Most striking of all, the great forests

0:39:100:39:13

that make Britain such a green and pleasant land.

0:39:130:39:17

But hidden beneath the surface is a secret world we barely know about

0:39:180:39:22

and that keeps most of Britain alive.

0:39:220:39:24

To find out how, I've come to Burghley Country Park in Lincolnshire,

0:39:280:39:32

where there's an oak tree in its prime.

0:39:320:39:34

And with enough space around its base

0:39:340:39:37

to explore exactly what lies below in a way I've never seen before.

0:39:370:39:41

Just like any building, trees have their own clever foundations

0:39:440:39:48

hidden beneath the ground to keep them upright.

0:39:480:39:50

We call them roots, of course.

0:39:500:39:52

And a tree like this will have the most substantial roots of all.

0:39:520:39:56

And for the first time, we want to reveal the root system

0:39:560:40:00

of such a majestic tree.

0:40:000:40:02

To do this, I need some help.

0:40:100:40:12

Sharon Hosegood is an expert at uncovering the secret life of trees.

0:40:120:40:17

Now, is this going to give us a pretty accurate measurement

0:40:190:40:21

of the tree's age?

0:40:210:40:23

It's as good as we've got without felling the tree,

0:40:230:40:25

-which would be absolutely awful.

-Wow, that would be little bit

0:40:250:40:28

extreme to get the age!

0:40:280:40:30

-6.3.

-6.3. It's a big 'un.

0:40:300:40:33

A girth of 6.3 metres makes this tree around 440 years old.

0:40:330:40:40

In other words, it was a seedling

0:40:420:40:44

when Elizabeth I had just come to the throne.

0:40:440:40:47

To explore these roots requires something very special.

0:40:500:40:53

Now, it might look like a pimped-up pushchair,

0:40:560:40:58

but this is a sophisticated piece of kit

0:40:580:41:01

that's going to let us peer into the ground.

0:41:010:41:03

Have you done any science on a tree of this significance before?

0:41:050:41:09

Not an oak. This is the biggest, oldest oak tree

0:41:090:41:12

that I know is being scanned in the UK.

0:41:120:41:15

Are you managing OK? I feel like I'm...

0:41:150:41:18

-Like I should help, or something!

-It's a one-woman job.

0:41:180:41:21

Tell me how it works. What's actually going on here?

0:41:210:41:23

Well, this piece of kit here, this tree radar looks like a pram,

0:41:230:41:26

but essentially, it's a ground-penetrating radar

0:41:260:41:29

which will pick up the roots

0:41:290:41:31

because they're full of water.

0:41:310:41:34

When we think about radar, we sort of think about aircraft radar.

0:41:340:41:37

We send out radio waves and they bounce back.

0:41:370:41:40

Is it doing the same thing as that?

0:41:400:41:42

It pretty much is. The principle's the same.

0:41:420:41:44

There's only a few of these in the world.

0:41:440:41:46

It'll show how deep they are, how far spread they are.

0:41:460:41:50

It picks up everything this diameter and above.

0:41:500:41:53

And to come here with this amazing, old, veteran tree

0:41:540:41:57

and to be able to see what's underground is a bit of a privilege.

0:41:570:42:00

'Sharon's got her work cut out.

0:42:020:42:05

'She goes round and round the tree in ever-increasing circles

0:42:050:42:08

'to well beyond where she thinks the roots will extend.'

0:42:080:42:12

Do we actually have a result? Am I allowed to see...?

0:42:170:42:19

We have a result. You are allowed to see it and here it is.

0:42:190:42:23

Oh, my God! That's great!

0:42:230:42:25

So here is the base of the tree.

0:42:250:42:28

And we can see the roots taper down quite quickly from the buttress.

0:42:280:42:33

I can't believe how clear it is.

0:42:330:42:35

I just thought it would be just a big mass of black

0:42:350:42:37

and you'd have to sort of tell me, "Oh, that's the root there."

0:42:370:42:40

But that... I mean, it's beautiful, isn't it?

0:42:400:42:42

Are these the biggest roots you've seen on a tree?

0:42:420:42:45

Well, this is certainly the biggest tree that I've scanned.

0:42:450:42:49

And I'm really pleased and surprised at the root density of this.

0:42:490:42:54

I mean, it was actually more than I imagined.

0:42:540:42:56

It shows that for a tree to be this old,

0:42:560:42:59

several hundred years old,

0:42:590:43:01

it needs to have a well-developed root system.

0:43:010:43:04

I'd like to go up to the tree and tell him,

0:43:040:43:07

-tell the tree that the news is good.

-Yeah, yeah.

0:43:070:43:09

-Tree, you're going to be OK.

-You're OK.

0:43:090:43:11

-We've done your medical, you're fine.

-Yeah.

0:43:110:43:13

You're going to live another 400 years.

0:43:130:43:15

'Enhancing Sharon's data, we can reveal how trees

0:43:160:43:20

'keep themselves upright

0:43:200:43:22

'in a very different way from, say, a building.'

0:43:220:43:24

The root system of our oak tree here

0:43:300:43:32

is likely to be one of the most impressive in the whole of Britain.

0:43:320:43:36

Some roots are as thick as a big branch.

0:43:380:43:41

And Sharon reckons the roots make up as much as a quarter

0:43:430:43:46

of the total weight of the tree.

0:43:460:43:48

The spread of roots underground

0:43:530:43:55

is even greater than the expanse of the branches.

0:43:550:43:58

A 30-metre crown,

0:44:020:44:04

and an even more impressive 34-metre spread of roots.

0:44:040:44:08

You might think the roots of such a tall tree

0:44:140:44:16

would have to go deep into the ground.

0:44:160:44:19

But even for such a massive oak, these are relatively shallow.

0:44:210:44:25

No more than a couple of metres deep.

0:44:250:44:27

In a way, the complete opposite of how you do foundations in a building.

0:44:370:44:40

So The Shard, which is very, very deep and very, very contained,

0:44:400:44:43

-here, you have shallow and spread out.

-Exactly.

0:44:430:44:45

And that manages the loading and it also helps the tree

0:44:450:44:48

get all the water and nutrients it needs from the soil.

0:44:480:44:51

Another reason why they tend to be shallow is tree roots need oxygen.

0:44:510:44:54

And the oxygen is found in the top metre or so,

0:44:540:44:57

before the ground gets too hard and consolidated.

0:44:570:44:59

So this is the perfect solution.

0:44:590:45:01

-Nature has found the perfect solution for the tree.

-It has.

0:45:010:45:04

'The roots are not only supporting the tree,

0:45:100:45:13

'they're also the tree's life-support system.

0:45:130:45:17

'The very reason why it could grow in the first place.

0:45:170:45:19

'Think of roots as more than just pipes

0:45:210:45:23

'drawing water out of the ground.

0:45:230:45:25

'There's something else far more interesting going on.

0:45:250:45:28

'Hopefully, I can see what that is.

0:45:280:45:30

'IF I can burrow under here.'

0:45:320:45:33

I'm actually under a tree.

0:45:360:45:38

This is a nearby tree that was growing onto a hillside

0:45:380:45:41

and then the hillside's just slipped away in a landslide,

0:45:410:45:44

revealing the roots underneath. And you can actually get inside.

0:45:440:45:47

You can see just how many roots there are

0:45:470:45:49

and how knotted and tangled it becomes.

0:45:490:45:52

But there's something else

0:45:520:45:54

that happens to roots when you're underground.

0:45:540:45:57

Let's have a little dig around here maybe.

0:45:570:45:59

I might be able to show you. Yeah, here we go. Now, look at this.

0:45:590:46:03

Hopefully, you'll be able to see this.

0:46:030:46:05

This, er...sort of white, stringy stuff that almost looks like cobweb.

0:46:050:46:11

That is what I'm interested in.

0:46:110:46:13

And that is actually a kind of fungus.

0:46:150:46:18

Fungi, which includes mushrooms, are odd.

0:46:220:46:24

They're neither plants, nor animals.

0:46:270:46:29

But they do have a nice trick.

0:46:310:46:33

Fungi break up dead plant material in the soil.

0:46:330:46:36

And this releases nutrients which the tree roots can then take in.

0:46:380:46:42

Without this process, the trees just couldn't grow.

0:46:440:46:47

But the fungi can't do that job alone.

0:46:480:46:51

They have some rather surprising helpers.

0:46:510:46:54

If you magnify soil 500 times, you'll see, hidden inside,

0:46:540:46:59

an army of microscopic animals and bacteria.

0:46:590:47:02

Working together, they're the ultimate recycling machine,

0:47:050:47:08

keeping the soil fertile.

0:47:080:47:11

So there's a whole, vast ecosystem underground

0:47:140:47:17

that's completely invisible to the naked eye.

0:47:170:47:19

And yet it sustains all of this,

0:47:190:47:21

the natural world we're so familiar with.

0:47:210:47:24

Today, there are around 100 million trees in Britain,

0:47:260:47:30

covering 10% of the land.

0:47:300:47:33

But there are far fewer forests than there once were.

0:47:330:47:36

We've cleared most of our trees

0:47:380:47:40

to make way for another living habitat.

0:47:400:47:43

One that covers over a quarter of the country.

0:47:430:47:45

Our farmland.

0:47:460:47:48

The distinctive patchwork of British fields looks familiar to all of us,

0:47:510:47:56

but sometimes, underneath, these, too, can hold surprises.

0:47:560:48:00

'You can't see what's down there,

0:48:020:48:04

'but there is one way to try to find out.'

0:48:040:48:07

Terry!

0:48:100:48:11

'Terry Herbert's been metal-detecting for over 20 years.

0:48:110:48:15

'And now, he's going to teach me how to hunt for buried treasure.'

0:48:150:48:19

Right. You've got a control box here.

0:48:190:48:21

You've got the VDI display unit.

0:48:210:48:24

You've got the coil, which finds you the items, that does.

0:48:240:48:27

That actually sends radio waves into the ground.

0:48:270:48:30

And if you hit a target, it comes back

0:48:300:48:33

and it gives you a reading on the meter.

0:48:330:48:36

Is it the type of hobby that you could give up your day job for

0:48:360:48:39

and actually make a bit of money on?

0:48:390:48:42

Well, you can do. I mean, some do.

0:48:420:48:44

On the beach, some people go to Spain and actually detect.

0:48:440:48:48

-You can earn quite a bit.

-Yeah.

0:48:480:48:51

So, what's the sort of most exciting thing that you've ever found?

0:48:510:48:54

Well, actually, the most exciting I ever found was a Saxon hoard.

0:48:560:49:00

It's the biggest haul of Anglo-Saxon gold and silver ever found.

0:49:040:49:08

In July 2009, Terry made the discovery of a lifetime.

0:49:100:49:15

An enormous collection of Anglo-Saxon treasure.

0:49:160:49:19

There were over 3,500 pieces

0:49:190:49:22

of decorated gold and silver buried underground.

0:49:220:49:26

I'm trying to imagine what it would have felt like

0:49:270:49:29

the first time you got a signal, like we're getting here,

0:49:290:49:32

and actually scrabbled around. And did you realise...?

0:49:320:49:34

You said it looked a bit like perhaps brass, or something.

0:49:340:49:37

Yeah. But at what point did you go, "Actually, no, that's gold"?

0:49:370:49:40

When I looked at it under me magnifying glass,

0:49:400:49:43

I noticed there was a pin.

0:49:430:49:44

So I thought, "Oh, this is a piece of gold."

0:49:440:49:47

I actually went back to me car and got me other machine out.

0:49:470:49:49

And, er...when I came back on the field with that,

0:49:500:49:53

it was just going off like a machine gun.

0:49:530:49:55

When archaeologists recovered the entire hoard and began to study it,

0:49:580:50:03

they realised the workmanship was exquisite.

0:50:030:50:06

Now it's considered one of Britain's most important archaeological finds.

0:50:130:50:17

The Staffordshire Hoard has been valued at a cool £3.25 million.

0:50:190:50:25

Terry received half of this, making him a millionaire overnight.

0:50:270:50:31

What happened to the money? What did you do with it?

0:50:340:50:36

I bought another machine.

0:50:360:50:37

I've actually bought three more machines, since then, like.

0:50:370:50:41

I think there's got to be another Saxon hoard somewhere in Britain.

0:50:410:50:45

No way have I just found the only one in this country.

0:50:450:50:48

There's got to be another one somewhere waiting to be found.

0:50:480:50:51

And it's going to take somebody with a metal detector to find it.

0:50:510:50:55

'Of course, the fields of Britain weren't cleared and cultivated

0:51:000:51:04

'just for Saxons to bury their hoards and for us to find them.

0:51:040:51:08

'They performed the very necessary task of feeding the country.'

0:51:080:51:13

And it seems every year, we demand the land produces

0:51:130:51:15

more and more food to put on our tables.

0:51:150:51:18

More than the soil can provide naturally.

0:51:190:51:22

And to find the magic ingredients to keep our fields fertile,

0:51:230:51:27

we've had to go beneath the ground once more.

0:51:270:51:29

I've saved the best till last.

0:51:370:51:39

Because here on the North Yorkshire coast,

0:51:390:51:41

I'm on my way to the deepest point you can reach under Britain.

0:51:410:51:45

OK, off we go. How long does it take to get all the way down?

0:51:490:51:52

-Takes about seven minutes, something like that.

-OK.

0:51:520:51:55

-Starting off slow and then we pick it up.

-Suddenly it speeds up!

0:51:550:51:57

This is Boulby Mine and it's the deepest mine in Britain.

0:52:000:52:04

And this lift shaft is over a kilometre straight down.

0:52:040:52:07

It travels at about ten metres a second.

0:52:070:52:10

Now we're getting to the bottom of the shaft.

0:52:120:52:14

'But the bottom of the shaft is just the start of my journey.'

0:52:140:52:18

This is so great. This is as deep as it is possible to go in Britain.

0:52:220:52:26

You can feel the wind, as well.

0:52:260:52:27

All the air that they're pumping in from up there.

0:52:270:52:30

There's a heck of a wind that comes down and just blows you.

0:52:300:52:33

'This is an amazing place.

0:52:360:52:39

'The mine is so vast, you've got to get around by truck.

0:52:390:52:43

'And I had no idea that the tunnels stretch out

0:52:430:52:46

'over five kilometres under the North Sea.'

0:52:460:52:49

It is an incredibly surreal experience being down here

0:52:510:52:54

because we're actually out to sea now,

0:52:540:52:55

we're actually underneath the seabed.

0:52:550:52:57

We've left Britain behind us.

0:52:570:52:59

And the tunnels just keep on going and going.

0:52:590:53:01

'It's a funny way to go to sea.'

0:53:050:53:07

We're 1,100 metres underground.

0:53:080:53:10

It's certainly the deepest place I've ever been in my life.

0:53:110:53:15

It's blisteringly hot, as well.

0:53:150:53:17

'The surface of the rock can be nearly 40 degrees centigrade.

0:53:190:53:23

'But what I'm really here for is what that rock contains.

0:53:240:53:27

'Now, it may not look much, but this is real buried treasure.

0:53:300:53:34

'And to get my hands on it,

0:53:350:53:37

'I'm going to operate this remote-controlled monster.

0:53:370:53:40

'Its jaws will do the hard for me.'

0:53:410:53:43

-So now you lift the head up.

-Ah.

0:53:450:53:46

Now, down a touch.

0:53:480:53:49

-So that's the head going down a bit.

-Yeah.

0:53:490:53:51

There we go, we're cutting in!

0:53:510:53:53

'These behemoths simple chew through the rock.'

0:53:570:54:00

This is what it's all about - freshly mined potash.

0:54:020:54:05

And it's this potash that they use to make fertiliser.

0:54:050:54:08

It's this stuff that reinvigorates the British landscape.

0:54:080:54:11

'They mine potash around the clock,

0:54:140:54:16

'carving out up to a million tonnes per year.

0:54:160:54:19

'This is the only place in Britain

0:54:190:54:21

'where we can get this valuable fertiliser.

0:54:210:54:25

'It's completely bizarre to think that down here

0:54:250:54:28

'is the stuff we need to put the food on our tables.

0:54:280:54:31

'But that's not all.

0:54:360:54:38

'They're mining for something else down here.

0:54:380:54:41

'Something strange and not of this Earth.'

0:54:410:54:44

Behind these doors, they're trying to get to the bottom

0:54:450:54:48

of perhaps the biggest mystery in all of science.

0:54:480:54:51

'Tucked away down here is Britain's deepest laboratory.

0:54:540:54:57

'And where you need to trade your green hat

0:55:000:55:02

'for a nice, clean, white one.'

0:55:020:55:04

-This is a full-on clean room.

-OK.

0:55:070:55:09

'Sean Paling is a physicist.

0:55:090:55:11

'He and his team down here are hunting for something mysterious.

0:55:110:55:15

'When scientists looked at galaxies in deep space, they found a problem.

0:55:170:55:22

'According to their theories, these spinning collections of stars

0:55:220:55:26

'should fly apart, but they don't.

0:55:260:55:29

'Something unseen is holding them together.

0:55:290:55:32

'Something they call dark matter.'

0:55:320:55:34

Dark matter is a name that we give to stuff that we think

0:55:390:55:41

exists in the universe that we can't see.

0:55:410:55:44

We think that when you look at the night sky,

0:55:440:55:46

the stars and the planets and galaxies,

0:55:460:55:48

the stuff that we know about makes up 15% of what's out there.

0:55:480:55:52

We think 85% of the mass in the universe is missing.

0:55:520:55:55

That's a lot not to know about.

0:55:550:55:57

Yes. I mean, it's an embarrassing lack of knowledge.

0:55:570:56:01

So far, no-one's found any trace of this dark matter.

0:56:040:56:08

Above ground, there's just too much light and radiation

0:56:090:56:12

getting in the way to detect it.

0:56:120:56:14

'But here, Sean hopes that the 1,000 metres of solid rock

0:56:140:56:18

'will stop any radiation from penetrating,

0:56:180:56:21

'but the dark matter will be able to get through.

0:56:210:56:24

'Down here is perhaps our best chance of detecting it.

0:56:240:56:28

'In our rapidly-changing world,

0:56:280:56:30

'it's knowledge itself that's become Britain's greatest resource.'

0:56:300:56:34

In making this programme,

0:56:380:56:40

I've seen a Britain I never knew existed. A hidden world.

0:56:400:56:44

I discovered what's underneath Britain's tallest building.

0:56:450:56:48

And ventured into a vast underground cathedral.

0:56:510:56:54

I've encountered the eccentric,

0:56:560:56:59

the surprising and the downright disgusting.

0:56:590:57:02

And I've seen the extraordinary ways that Britain below ground

0:57:040:57:08

has affected and shaped the countries and cities above.

0:57:080:57:11

And next time...

0:57:130:57:14

..I blast my way back underground.

0:57:170:57:20

And take to the skies

0:57:200:57:22

to reveal the secret networks and connections

0:57:220:57:27

that keep Britain moving.

0:57:270:57:29

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