Episode 2 Britain's Lost World

This is the wildest, most remote part of the British Isles.

It's called St Kilda.

A handful of rocks out in the Atlantic Ocean

over 100 miles from the mainland,

it's the most secret place in Britain.

Home to sea birds and seals, these islands are also a place of mystery.

Until just 80 years ago,

St Kilda was inhabited by a race of people

who lived in an extraordinary way.

But when they suddenly abandoned their homes,

they left behind a place full of secrets.

St Kilda is Britain's very own Lost World.

Today, historian Dan Snow, naturalist Steve Backshall

and me, Kate Humble, are going to venture there

to explore, to experience and to unravel the secrets of St Kilda.

It's been a tough assignment.

But we've already found out about where the St Kildans lived,

the extraordinary way they caught the sea birds...

This is a really effective way of moving around the rock face!

'..and just how precarious their lives were here.

'We've traced human settlement back to the Vikings

'and seen how St Kilda's favourite resident is faring...'

Oh, look at you, little thing!

'..but there's so much more to discover.'

Our expedition continues. We're going to be going further,

exploring where few people have been before on these remote, stunning islands.

'We'll be diving into St Kilda's stormy seas,

'discovering Britain's most secretive bird...'

-Yep, can you see?

-Ah-ha, yes!

-Go!

-'..doing the St Kilda Challenge...'

Here's Dan! Come on, Dan!

'..and taking on the island's most dangerous intruder...'

Oohh!

'..all to unlock the secrets of Britain's lost world.'

'Welcome to Camp St Kilda,

'three little tents perched on a hillside

'on Britain's most remote island.'

Come on, Kate, time to get up. I'm going to put some porridge on.

Look at you, Mrs Beeton!

-HE SIGHS

-Hey, dude?

-I'm all right.

Another day in paradise.

'We're nearly halfway through our mission.

'But there are still many mysteries to solve, both ancient and more modern.'

Ohhh! What a beautiful day!

In 1930, St Kilda was abandoned by the people who lived here.

Since then, this cluster of rocky islands has become a dual World Heritage Site,

not only for its history, but also for its astonishing wildlife.

It's watched over by the handful of National Trust experts who spend their summers here.

It's like a place that time forgot,

left to the birds, the wind and the wildlife.

But how is St Kilda's wildlife surviving in the 21st century?

'We've already explored the flourishing gannet colony.

'Now I want to see how St Kilda's marine life is doing.'

-Hi, how are you doing?

-Hi.

'So I'm heading out to sea.'

The waters around St Kilda are rich in wildlife.

Throughout the year, you might see large mammals like minke whales,

porpoises and dolphins,

and North Atlantic grey seals.

But for my dive I'm aiming for some of the smaller delights on offer.

I'm joining marine biologist Dr Graham Saunders

on our specialist dive boat, and we're hoping to see some real gems.

-Graham...

-Hi, Kate.

-How are you?

-I'm fine, I'm fine.

-Good. You've been looking at the map?

Well, given the conditions, the fact that this is rather an exposed area...

-Yeah.

-..as you probably know...we're probably going to go in somewhere along here,

because the wind will, as normal, cause a problem if we were out on the west side.

-OK.

-So, here's Village Bay...

-Yeah.

-..and here's a place called Sorca.

-Right...

'Because the waters around St Kilda are so rough, very few marine surveys have been carried out here.'

I mean, you've done an awful lot of surveying

of marine life around the west and north coast of Scotland,

but you've never made it here before, I gather.

I've tried, I've tried to get here, this is my fourth time.

The other three times I got almost halfway here, the weather came in, and I was turned back.

Now as far as wildlife in, as you say, a really exposed,

remote little archipelago that we have here...

I mean, do you imagine it's gonna be very different

from what you'd normally see, say, on the west coast, when you're surveying?

We are getting some of the benefit from the North Atlantic drift,

so the water is marginally warmer,

but it does mean that some of the species that would normally inhabit the northern areas

are just about starting to get in down here,

whereas some of the southern species from way down to southern England

and even as far down as the Mediterranean...

-Yeah.

-..penetrate up here too.

'Graham specialises in some of the smallest forms of sea life,

'and that's what we're hoping to photograph on our dive down.

'But while we've been inside the ship's cabin,

'the weather has got worse.

'As our skipper moves us into position, it's clear how much the swell has picked up.

'It shows how fast conditions can change out here.

'If we don't dive now, this could be failed attempt number four for Graham.

'In water this cold, there's a lot more gear to get used to,

'not to mention the equipment needed to photograph the sea creatures.'

AIR HISSES

'With the swell increasing, after one last safety briefing it's time to get us into the water.

'Graham and our cameraman safely take the plunge.'

Have you got it?

'But just as I'm about to step off, our safety man stops me.'

Hold on, hold on!

'The strong current has already swept our cameraman off course,

'and it could be too dangerous for us to dive in these conditions.

'It's pretty nerve-racking, but we'll have to reset and give it one more go.'

'Life on St Kilda has always been dominated by the wild, changeable weather.

'There are reports of islanders left deaf for days due to the noise of the storm winds and waves,

'it could be that ferocious.

'Often trapped in their houses for weeks while winter storms savaged the island,

'the entire village was once destroyed in a gale.'

The wind's getting up a bit. I think we're reaching the point

at which this slope turns into one of the biggest sea cliffs in the UK, so be careful.

'The islands are battered by the weather rolling in off the Atlantic,

'but they make their own weather too.

'When sea air hits these cliffs, it creates a micro-climate.

'Average rainfall here is double that of the mainland.'

SEA BIRDS CALL

Pretty much the most extreme weather in the British Isles up here.

The wind, although there's not much blowing today, about two or three knots of wind today,

can get up to... The highest recorded wind speed was 140mph, it's absolutely unimaginable.

That kind of wind would simply pick me up and blow me off this cliff.

And frequently, sheep do get blown off the cliff.

The St Kildans actually got pretty good at forecasting the weather. I mean, their lives depended on it.

They'd look at where the birds migrated on the island, to give them hints

about where the next weather front might be coming from.

Also by looking at the sea, of course...

Big, crashing waves on the east side of the bay here mean bad weather,

even if the weather is fair.

But waves crashing on that beach means it'll probably stay fair.

So today, looks like something might be brewing.

We've got our cameraman safely back on board

and are about to give diving another go before the weather gets even worse.

-HOOTER BLASTS

-OK...

A big swell above water usually means strong currents down below.

This could be tough going.

Graham and I are particularly looking for any species

that might show if the waters here are getting warmer due to climate change.

Even on a day like this the waters are exceptionally clear.

Dense kelp forests loom out from the depths,

beckoning us towards the steep underwater cliffs of Doune.

But as we get closer into the narrow gully, the conditions worsen,

throwing us back and forth, making any work here almost impossible.

So we have to get deeper, under the cliff face, and away from the swell.

Then we can steady ourselves and get our first glimpse of what St Kilda has to offer.

It's astonishing to think that such delicate sea life can exist

miles out in the wilds of the Atlantic.

But it's really hard work struggling to stay steady in these currents.

That means we're using up air at a faster rate than usual,

so we have to go up earlier than planned.

We surface some distance from where we started.

All I can think about now is getting out of the strong currents and safely on board.

A lot of swell, a lot of surge... Hopeless!

The expression commonly used is "like being in a washing machine",

-and it WAS just like being in a washing machine.

-It was just hell!

'It's time to dry off and look at the pictures we've taken.

'Did we manage to film anything unusual,

'or did the conditions simply make it too difficult?'

I was quite surprised, because you sort of look and think it all looks

like that slightly sort of blotchy kind of algae and small seaweed.

But when you start to look, there are some real jewels there, aren't there?

Yes, there are. Just underneath the kelp you'll see

that the rock itself is absolutely covered in life.

Look! You get a real sense that we are being battered about there.

These poor anemones are being absolutely walloped by the surge.

Everything is flying about.

Almost everything here is actually adapted for just hanging on.

Right. This is where I saw this fantastic nudibranch, this sea slug,

that was very inconveniently (a) exactly the same colour as the kelp,

and (b) right in amongst it,

so all those fronds were passing right in front of it.

-It IS like a dragon. I know you think I'm mad, but look, it just sort of...

-Yeah.

And that weird, spirally shell on there...

'This little beauty turns out to be a sea hare with a rather unusual visible shell.'

I'm really pleased with that find.

I did spend quite a lot of time just trying to get some nice shots

of the jewel anemones, just because they are so colourful.

They're beautiful. I think people just don't expect to have that sort of colour in cold water,

in British seas, but there's a lot of really beautiful stuff down there.

That is a southern species,

but it's made its way up here and we see them in large numbers up here.

Would you say that's an indication of a warming sea,

as something that's symptomatic of climate change,

or is it because St Kilda is on the North Atlantic Drift, you've got these warmer seas,

you can have these southern species existing happily up here?

-Yeah, I think the latter there is the correct one.

-Right.

The water is relatively warm here, the North Atlantic Drift.

And so these kind of anemones proliferate.

'So from the species we saw,

'it seems that St Kilda's amazing underwater wildlife is thriving.'

These remote islands are a treasure-trove of history as well as wildlife.

Because St Kilda has been almost abandoned for 80 years, it's like an archaeologist's dream.

Relics of the past lie untouched, and just waiting to be discovered.

During the Second World War, no less than three Allied planes crashed on St Kilda.

I've come to Glen Mhor, on the north side of Hirta,

to try and work out what happened in one specific case.

The night of 7th June 1944,

ten crewmen were flying their Sunderland flying boat on a training exercise,

and it crashed here on St Kilda.

Now the interesting thing about it is that other Second World War planes crashed all the time,

but their wrecks were immediately picked apart by souvenir hunters and so on.

But here on St Kilda, it's so isolated - no-one was living here at the time -

large parts of this wreckage are supposed to be in this valley here.

As you'd expect, lots of wreckage I think rolled down the hill

and congregated towards the bottom of that glen, so I'm gonna head down there.

Nobody knows exactly why this Sunderland flying boat crashed here.

If I study the pattern of the wreckage, maybe I can work out what happened.

Sunderland flying boats were RAF reconnaissance aircraft that protected Allied convoys at sea.

By 1944, they had powerful engines, machine guns, and even radar,

making it even more surprising that the plane crashed here.

It was an absolutely miserable night, even though it was June.

They couldn't see, the visibility was 300-500 yards, apparently,

and they were flying their last training mission.

It's actually tragic, in a way. It was ten guys. Seven New Zealanders,

three Brits and an Aussie,

and a very experienced pilot, very experienced co-pilot.

The pilot actually had about 800 hours of flying - very experienced.

He'd actually flown this precise circuit before, at night.

They were on their last training run and knew these parts,

and they were to be posted to North Africa to protect convoys,

which actually by 1944 was quite a cushy job, so they're safe,

so it's very tragic that they came up here and crashed.

Oh, yeah, you can start to see pieces here now.

Up close, suddenly it's all becoming a lot clearer.

There's two, three, four pieces there...

Oh, look at this. Wow!

God!

This is incredible! Oh, my God!

-RUSH OF WATER

-It's absolutely gigantic!

Wow!

At the risk of sounding like a total idiot,

I think this might be some kind of turret here,

because it definitely seems to be on a swivel.

And in fact, yeah, this...

Yes, in fact it is, because I'll tell you what,

these are the brackets for the 303s,

the machine guns that would be the defensive armament.

This is incredible here. This would probably be the turret on top of...

In fact, I have a plan here, let me get it out.

..the turret on top of the fuselage with these 303s mounted,

obviously to protect the flying boat from enemy fighters.

Here you have the machine guns up here, in the front here, and aft,

these aft 303 machine guns.

And those are quite clearly the machine-gun mounts

so I never expected to be able to identify a piece of aircraft, and the first bit we've come across.

It's absolutely fantastic.

I think this is Tail End Charlie's seat.

Incredible. Let's keep going,

see if the beginner's luck keeps holding up.

Some pieces here, looks like fuselage, I'd say,

just twisted and obviously blown in here and then just got wedged under this rock.

Imagine a piece of metal this big cartwheeling across the hillside,

it's absolutely incredible.

What's this here? Looks to me like it's just some pieces of fuselage.

Wow!

One of the propellers. There were four engines on this Sunderland,

and this is obviously one of the props, and this is fascinating,

look, you can see it's been buried, or it's buried itself, conceivably,

and now slowly it's just...

The ground is being eroded away to reveal this incredible find.

All slightly bent, presumably as they hit the ground.

'Climbing to the top of the glen, I think I'm closing in on the main wreckage site.

'But does where the plane crashed give us a clue as to what happened?'

It's very hard to see why the pilot would make a mistake,

perhaps underestimating the height of St Kilda.

Clearly the weather was bad

but there must have been an element of equipment failure, instrument failure.

Right, this is the top of the ridge here, pretty windy, and you can see

what they were aiming for - just this lowest point of the saddle.

But I'm pretty sure this is the main crash site, and they didn't make it.

They were close, though. It's really tragic when you come up here and look at it.

There's a lot of wreckage here, including some pretty big parts.

This looks very clearly like the place when it went in.

Gosh.

Well...

A piece of engine.

Goodness me. You can see there's a sort of crater here, it's just hit straight in like that.

Wow!

And now that I'm standing here, it's just a matter of metres.

It must have flown straight up this valley, been surprised by it, pulled as much power,

given it as much stick, as they could, and they just couldn't edge over the ridge line there.

It must have been 15-20 seconds of...unbearable terror.

And then they went straight into the hillside.

'It was night-time, and the weather was atrocious.

'Even so, I think that equipment failure must have played a part in this tragic crash.

'Otherwise, it's hard to see how an experienced pilot could make a mistake like this one.

'Because of the terrible weather, it took over two weeks for a rescue party to reach St Kilda.

'One account describes finding the body of a crewman who had survived the crash and taken shelter,

'but the rescuers came too late.

'In the end, all the men of Flight ML858 were given a burial at sea,

'just four miles from this hillside.'

St Kilda's connection with the military became formal a few years later.

In 1957, the Ministry of Defence set up a radar tracking post here.

There's been an MoD base here ever since.

But how well do the military and the wildlife coexist?

I've been called to the base for an emergency, which may tell us more.

-Whereabouts is it?

-It's just behind the steps...

'A rescue mission is under way

'and I join National Trust wildlife warden Sarah Money to lend a hand.'

Oh, yes.

-Oh! Head tucked under its wing.

-I know.

'In late summer, young birds on their first flight

'are attracted by lights from the base and crash into the buildings.'

No, don't go for me. Look, I'm rescuing you, just be grateful.

SHRILL SQUAWKING

All right, all right, all right, all right.

-That's what they sound like normally.

-I've got you.

I've got you... I know, I know.

'This disoriented chick is a Manx shearwater.'

How handsome are you?! You're not grateful at all, are you? Come on, in the bag with you!

No, no, no don't savage it.

-I know.

-SQUAWKING CONTINUES

Put it down!

'The chick doesn't seem to realise we're doing it a favour.'

SQUAWKS OF PROTEST

-Well, he's rescued, hurray!

-He is.

'The bird is fine - just a bit cross.'

It's time for this feisty little Manx shearwater

to be released, Sarah, so what's the best way to do this?

Right, if you get him out the bag the same way you picked him up...

-Yeah.

-..with the hands around its wings to control them...

Shall I hold the bag...? There we go.

-OK.

-Then, I'd just point him out towards the sea...

-OK.

And just let him have a view of what he's gonna do.

-So shall I go right down to the edge there?

-Yeah, if you do...

You're desperate to go, aren't you?

So, no nasty-looking skuas around?

-No, hopefully not.

-Just fulmars.

-And then you're gonna just wait for a little gust of wind.

-Yeah.

Just launch him, and he should fly straight out.

-That's a good gust, yes? Ready?

-Go for it!

One, two, three, go! Woo-hoo!

Don't fall in!

-Ohh!

-Doing well.

-That's fantastic.

Well, thanks, that was a huge honour.

'The shearwater's not alone in needing to be rescued.

'Every summer, many young birds make the same mistake.

'But, as in this case, there's generally a happy ending.'

The handful of men at the MoD base

are now the only people who live here all year round.

But they are surrounded by the relics of centuries of human life.

The houses of the last St Kildans still stand in the village,

and there are over 1,000 of these unique stone storage chambers,

known as cleits, scattered across the hillsides.

There are also some even more extraordinary hidden structures,

and I'm going to go and look for them, with Steve's help.

As a tiny isolated community, St Kilda was always vulnerable to attack from the sea.

Vikings, pirates, and even a German U-boat in 1918, all came here on the offensive.

But the St Kildans had their own method of defence.

Must have been absolutely terrifying seeing a strange ship pull into that bay.

I'd have thought any kind of contact for these people would be bad enough,

but if it was the Vikings or someone that could do you serious damage, that would just be horrific!

I think they had to assume that any ship they saw was hostile,

because they couldn't risk all being caught here in the village and slaughtered,

all the women being carted off, or all their stuff being taken.

So what would a society like this, with no real fighting force,

do against someone like the Vikings?

No chance. The Vikings were some of the most incredible warriors ever,

so you can either fight them or you can run. Fight or flight.

They wouldn't fight the Vikings, they're too few, they're not trained warriors.

So we reckon basically they charged into these hills and found hiding places.

And there's basically some dugouts, almost, in that scree,

so I'll go up and have a nose about.

I can't believe for a second that there's anything up there to hide a 6'6" bloke wearing bright blue.

Bright blue... You'd be surprised!

Here's the scree slope.

Uh... Nice and wet.

'I'm looking for shelters that are unique to St Kilda,

'secret hiding places built into the hillside, that are very difficult to spot.'

So that's not what we're looking for.

It can be very hard to tell in these scree slopes what's man-made and what's not.

This one here is certainly man-made. I think this is more of a cleit.

Looking at it, you can tell, the regular stones piled up.

Clearly man-made, filled up with a bit of rubble, this could've been an original,

but it feels more like a cleit, this round shape.

Let's see if we can find one that's definitely a hidey-hole.

Whilst I continue my search, Steve's keeping an eye on the slope to see if I can really disappear.

STONES RATTLE

-RUSHING WATER

-No. Still see him... It's never gonna work.

Right, what have we got here?

Ah, right, now this feels definitely very different to a cleit.

The ones I've seen here have all been raised above the ground,

they've all been circular, keep the air flowing, keep the stuff in them dry for the storage.

This is a trench, it's dug in, it's damp down here,

and one thing it does do is keep you very, very out of vision

to anyone down on that beach, like Steve.

All right, Steve, can you see me now?

Unbelievably, Dan, no, I can't. Where have you gone?

I can see you, buddy, so don't come marauding in my village.

How big is the hidey-hole you're in at the moment?

You could fit a decent-sized family in here, I think,

five, six, seven people in this one.

It wouldn't be comfortable for long, but you could get them all in.

And what's the view like up there?

Would you be able to see people coming in, is it a good place to spy from?

'Yeah, you can see the whole bay, the beach, the whole village,

'and you can see a good 20-25 miles out to sea, to be honest.

'So it's a fantastic place, actually...'

Since I've been up here, a boat has actually sailed into the harbour,

and it's quite poignant seeing that sail a long way away

and it's getting closer and closer

while I look for these hidey-holes.

It just reminds you what was at stake for those guys.

Any sail represented serious danger.

STONES RATTLE

While people have come and gone over the years,

the animal life here has remained remarkably distinct from mainland Britain.

There are no dogs or cats or rats here,

no frogs, no foxes and no rabbits.

There are sheep, though.

Blackfaces descended from the ones the St Kildans left behind when they evacuated,

and wild flocks of brown Soay sheep, which are a native breed.

There's also one small native animal here that's a bit special.

And this is the only place in the entire world that you can find it.

Isolated island chains like St Kilda are fantastic places

for studying evolution in action.

The Galapagos and Charles Darwin would be a perfect example.

The thing is, animals get stuck here and trapped from the mainland

and develop very differently from their cousins way back over there.

And here on St Kilda, it's not happened a tremendous amount,

because most of the animals that are exciting that live here are birds.

There is, however, one exception.

Erm, it's a mouse.

But what makes the St Kildan field mouse different from a mainland field mouse?

In order to find out, I'm going to set up some friendly traps.

Bit of apple here.

Also some peanut butter. I'll slap that on there,

put it into the trap,

and place some cloth inside to function almost like bedding, keep the mouse warm,

place the trap in there... and load it. Right, it's good to go.

Some hours later,

and I've called on the help of wildlife warden Sarah Money

to help unload the traps.

First signs are, there are plenty of mice.

Six traps, all six of them sprung, although this one here, Sarah,

appears to have had a kind of mighty mouse inside it.

-Yep, a supermouse in there that's managed to wrangle his way out quite well.

-Yes.

-Shall we see what's happened inside the others?

-Yep.

Really, we're thinking these must just be St Kildan field mice.

That's the only small animal we've got here, so hopefully they are.

-OK. Let's see what we've got in this one here...

-OK...

RATTLING

-SHE LAUGHS

-Sadly, mighty mouse has struck again, and this trap's empty too!

And this one.

-And, believe it or not, this one too!

-HE LAUGHS

These mice must have evolved into some kind of rodent Houdinis!

BOTH LAUGH

OK, this one feels quite good.

This one feels quite heavy.

RATTLING

Oh, he's trying to get out the other way!

OK, there we go.

So there we have our first St Kildan field mouse.

He's very, very, beautiful, isn't he?

They are, they've got much longer, fluffier fur than the mainland ones,

-and quite a long tail as well.

-Yeah.

OK. Right, well, shall we weigh this one

-and have a little look at how it's doing?

-Yes.

So that's about 80g, so it's only about 30g, which means it's either a youngish female

or it's a young from this year - the young start appearing in traps in late June.

That would still be big for a mainland field mouse.

Yep, for a mainland field mouse that would be a big mouse.

Maximum is about 29g, but St Kilda field mice get up to about 55g, so it's a small one.

There you go... He's a little bit stressed

so I think we should release him into one of the walls.

-Yeah, release him into the stones?

-Let's try this wall up here.

The second I put this down, he'll disappear at a phenomenal rate...

-BOTH: Whey!

-Off he goes!

-Great stuff. Very beautiful little creatures.

-Wonderful.

They're nice to live with, I've got a few at home.

Its isolation means that the St Kildan field mouse

has taken a different evolutionary route to the mainland field mouse.

At nearly twice the size of its mainland cousin,

the St Kildan field mouse really is a mighty mouse.

There are few places in the world

where history is written so vividly on the landscape as St Kilda.

We already know that people lived here

as far back as 1,200 years ago.

But did people live here even earlier than that?

One particular remain here that I want to check out, it's called the House of the Fairies,

which shows that the people living here on St Kilda knew that it was old, almost mythically old.

One small problem is that all these cleits and all these houses look exactly the same.

'Luckily for me, some conscientious archaeologist has drawn up a plan, with each house and cleit numbered.'

Every single stone building marked out, it's fantastic.

Should be no trouble finding this site at all.

Unfortunately, it is through the marsh.

Ugh!

Probably should have gone the easy way. That's 84...

that's 83...

82, 81...

This one shouldn't be here... ..75...

Ah-ha! Here it is.

Wow, yeah, now this is a completely different type of remain here.

Oh, yeah, this is great.

It's underground, it's damp in there, it's full of puddles,

not a house, definitely not for storage, let's go in.

'But what is this structure?'

Ha-ha! It's pretty dank in here.

Yeah.

There's a little side passage round here.

Torch...

OK, it's pretty small in there, it's not clear what it does,

perhaps there's been a collapse. I'll see if I can get in there,

have a little look at things.

HE GASPS

There's wonderful big slabs of rock here and they make up the roof.

Now there's possibly been a collapse at the end,

but you can clearly see these enormous lintels, this sort of roofing here.

Huge effort, to create something like this.

Right...

'I'm beginning to think that this is a burial chamber.

'But how old is it?'

Goes in about another five metres, I suppose,

and then it stops, it looks like another collapse here.

Of course, this tunnel might go a lot further in, that's very exciting.

But look at these stones here!

These are actually the biggest building stones that I've seen used anywhere in the village.

Some of these are gigantic,

so whoever built this was...had the ability to move these.

I've been in chambers like this in Ireland, in southern England, and it's amazing to think that here,

right out at the north-west extremity of the British Isles,

there's still that same culture of digging tunnels

and using rocks like this to create, perhaps, burial chambers and stuff.

It does seem to prove that there have been people here on St Kilda for at least 2,000 years.

'It is astonishing that somewhere as remote and harsh as St Kilda

'could have been home to humans for so long.

'But could people have been living here even earlier than that?'

These places just aren't really built for people my size.

We're now halfway through our time here,

and I'm more intrigued by this wild place than ever.

It is extraordinary, and it's still just as extraordinary now, a few days in,

that I'm actually still in the British Isles.

It's a very, very strange place, and the weather can change in a heartbeat.

So one moment it can look very benign and blue and sparkly,

and the next minute it can be like this, where the weather's completely closed in

and you can barely see your hand in front of your face.

You never know what to expect.

It still feels like it's got this sort of strange, primeval pulse.

It still feels very alive and kind of mysterious,

and I think you could be here for months and months and months

and never quite get to grips with it.

As a historian, it's been fascinating because

there's so many levels of history here in this confined space.

It's isolated, so we can identify different periods of its history, all these layers.

The difficult thing, though, has been, because only one tiny part of these islands

is suitable for habitation,

all the history is piled on top of each other within a couple of acres

just down there in the village. So that's been really exciting.

I've wanted to come to St Kilda for a very long time, since I was in my teens,

and it had an awful lot to live up to.

You only get a taste of the real extremes of a place from what you hear before you get there.

But it's really lived up to my greatest hopes, I think.

Even beachcombing here is an adventure.

You can find things on St Kilda that you'd be astonished to come across on the mainland.

I was hoping to catch a glimpse of a passing whale,

but instead I've come across a poignant reminder of their presence.

Well, I smelt this long before I saw it.

It's rather a macabre reminder of the amazing things that live in the waters around St Kilda.

You can see instantly it's a whale of some kind.

This has vertebrae, backbone and ribs, just like we do.

And looking at the jaw bone here,

you can see the sockets that once held its teeth,

so it's not a baleen whale, it's not a minke whale.

From the length of it, the tail over there,

probably about 12, 13 feet long, a good-sized animal.

I reckon that this was once a pilot whale.

Unfortunately now, though, just food for the gulls.

SEA BIRDS CRY

St Kilda is world-famous for its extraordinary bird life,

the puffins, gannets and fulmars

who've nested here for thousands of years.

But there's a newcomer who's making its presence felt.

Down here is possibly one of the most dangerous parts of the island.

This ridge overlooking the whole of St Kilda is home to the great skuas.

It's been nicknamed Bomb Alley because of the birds' terrifying behaviour.

Great skuas have a reputation for terrorising other sea birds,

forcing them to drop their catch.

And those are the lucky ones. The others, they kill.

This...um...rather fetching garment is a tea cosy,

and I'm assured by the people at the National Trust who work here

that this is the best defence against one of the biggest, nastiest birds in Britain.

I'm ready!

BIRD SQUAWKS

Whoo! Ha-ha-ha!

Oh, here comes another one...

Ah!

Ooh... Ha-ha-ha!

Skuas came to St Kilda only 30 years ago, from the Western Isles.

As you can see, they're not at all keen on human company.

But are skuas just thugs like East End bouncers?

Well, of course they're not.

I'm going to take this off out of respect,

because they are ground-nesting birds... I've got a chick right here.

..and like any good parent, they're protective of their young,

so that's why they will dive-bomb anything coming into their territory.

Traditionally, great skuas live off fish,

but as fish stocks reduce they must look elsewhere for their dinner,

even if it means a spot of cannibalism.

This is what can happen to a skua chick

if both parents are forced to leave it and go and look for food.

Skuas are incredibly opportunistic,

and if they see easy pickings like their neighbour's chicks, they go for it.

It seems extraordinary that they would even eat their own species,

but all the great skuas are doing is ensuring their own survival.

There are now 200 breeding pairs of skuas on St Kilda,

but they may be thriving at the expense of others.

I'm on the search for a much rarer bird than the skua -

the Leach's storm-petrel, Britain's most secretive bird.

St Kilda is home to an important colony of them, and I want to find out how they're doing.

I'm joined by Sarah Money, the National Trust warden.

These birds are tiny. They spend all day out at sea, and they nest at night in deep burrows.

No wonder I've never seen one.

BIRD CALLS

Sarah has a trick up her sleeve, though.

BIRD CALLS AGAIN

So, Sarah, can you explain to me what you're playing out of that?

It's a Leach's petrel male chatter call. So it's a Leach's petrel from St Kilda.

It's a male. We're playing it to get males who are nesting in burrows amongst the rocks to respond.

BIRD CALL PLAYS AGAIN

-Do you know what, I can...I can hear something over there.

-Yep.

If we head over there...

BIRD CALL PLAYS AGAIN

So why would the males be responding to this call here?

They think it's an invading male,

so they're saying, "Right, this is my burrow, leave me alone!"

BIRD CALL PLAYS AGAIN

And at the moment, the males are inside the burrows, sitting on eggs?

Yes, some of them might be on chicks, but most of them are just sitting on eggs.

-There's definitely one just over here.

-I know.

BIRD CALLS

-Oop. Heard one behind there!

-That's wonderful!

-ANOTHER BIRD CALLS And here...

-What an unbelievable noise!

So they're talking to this, and he's talking to that one over there.

CALL PLAYS

BIRD RESPONDS

-There we go.

-Wonderful!

-He's right down at the base...

-He's very, close, isn't he?

-Yeah.

Now we've found a nest, Sarah has some more specialised equipment to study the birds in detail.

-Endoscope?

-It is, yeah, I hide it in this cleit, just stored in a survival bag and left up here.

-Cos it's so big, we don't want to carry it up every time.

-Right.

'More commonly found in hospitals,

'this endoscopic camera will help us confirm that there's a bird in the burrow,

'and let us take a closer look at the bird itself.'

So what are you actually hoping to achieve by looking inside these burrows?

We're trying to find out things like egg-laying date and hatching date,

how long it takes the youngs to fledge, the growth rate,

how often the adults go in to be with the youngsters as well.

Just as much information as we can get. Because it's a tiny bird, comes in at night,

lives in a deep burrow, not much is known about them,

so any information is wonderful.

Now, you've marked it here. Where does the burrow actually go?

I can't see an entrance, nothing!

The burrow entrance is just down here, and it's not very obvious,

but the burrow goes up there and they tend to nest under the rocks.

So we just pop that in the burrow entrance

-and you see this sort of grass...

-Yeah.

..and move it around a bit and...

just check we're going in the right direction.

I'm just wondering if that's an egg.

-I can see something.

-Or a bird, even.

There's definitely something.

-Is that nesting material?

-It is, I think, yep, can you see?

'It's a tantalising glimpse,

'but this bird is too deep underground to take out and get a really good look at.

'In order to see one, I'm gonna have to join the night shift.'

'It's now 2am, and whilst the others are all tucked up in their tents, I've joined Will Miles,

'who's been studying the Leach's storm-petrel almost every night for months.'

BIRD CALLS

'Now the birds are active, Will uses the recording to lure them into a fine mist net.'

Just open the net and lift it out of the pocket like that...

Oh, look at that, that's beautiful!

Shall we go in and ring it?

-Let's do that.

-Yep.

'At last, my first chance

'to see St Kilda's very rare Leach's storm-petrel.'

This is a very significant population of Leach's storm-petrels?

Yeah, in British terms, it's thought that up to maybe 95%

of the British and Irish Leach's petrel population is breeding here on St Kilda,

so that is maybe a maximum of 45,000 pairs.

'These birds spend almost all their lives out at sea.

'They're only coming into land now because it's the breeding season.

It's a real privilege to see one so close up.'

164mm.

'It's thought that their numbers are declining, and part of Will's study is to try and find out why.'

82g, with the bag,

and the ring number is 58474.

No sooner is the information gathered

than it's time to let the petrel go.

-BIRD THUDS Into the ground.

-And around a bit.

And then straight up into the sky.

-And off it goes!

-Away out to sea.

'Will has come up with a theory on why their numbers may be going down.

'He believes the clue is in these pellets

'regurgitated by the island's most aggressive inhabitant,

'Kate's old friends, the great skuas.'

I can't believe these have been regurgitated, that's incredible!

There really is nothing that these birds won't eat, I mean they're eating razorbill heads whole.

All the brains and eyes have been taken out, probably digested,

and that just comes straight back up.

And...well, you can tell what that one is - there's no guessing, that's definitely a puffin.

-And this one here, is that guillemot?

-Yep.

That looks about the right kind of size for one of ours, isn't it?

Yes, this very, very, tiny little skull

with a very delicate little black beak.

It's a Leach's petrel.

'Although larger, more common birds have obviously also been eaten,

'the great skua seems to find the Leach's storm-petrel a particular delicacy.'

Two tiny little feet sticking out the bottom of a pellet,

that really is rather macabre, isn't it?

Any idea what that would be?

These are, again, Leach's petrel feet.

Right, OK, so there's really no doubt, then, that the skuas are definitely eating...

Yeah, they really have a go at the petrels.

'Even though the Leach's storm-petrel only returns from sea in the middle of the night,

'it now seems likely the great skua hunts them at night as they try to enter their burrows.

'Will reckons the skuas are making a real impact on the population of Leach's storm-petrels.

'It may be that St Kilda's newest resident is now endangering the survival of one of its rarest.

'Let's hope there are still storm-petrels on St Kilda in years to come.'

In our time here so far,

we've found out a lot about this unique wilderness.

These little islands, far from the mainland,

have been almost untouched by humans for 80 years.

We've seen how the wildlife under water is thriving...

I'm really pleased with that find...

..and how St Kilda's very own species of mouse is doing well.

He's very, very, beautiful, isn't he?

St Kilda's isolation means that its history lies preserved,

in ruins and fragments on the ground.

We've traced back human life here till the Iron Age.

And we've solved the mystery of a more recent tragedy.

There must have been an element of equipment failure, instrument failure...

Now it's time to put ourselves to the test - well, not me, actually, just the boys.

The people who work here have found a novel way to keep themselves fit,

and take on St Kilda's intimidating landscape.

-So are you guys ready?

-Not really, no!

-No!

-We spent our day absolutely terrified...

'Timekeeping will be conducted by female record holder Sam Dennis.'

-What are you making us do?

-It's the chimney run.

Modern tradition. Army guys used to do this all the time,

and we've got to keep up that tradition.

-Start here, head for the chimney...

-Oh, my God!

-..to the top...

-Oh, my G...!

So I've come up here first, because obviously I didn't want the boys to be beaten by a girl,

because it would just be too embarrassing for them.

But Dan and Steve are going to do the proper race.

They're gonna race round the bay here,

which as you can see is a gentle slope upwards, just to get them in the mood,

cross the helipad, and then up this ludicrous slope.

-It's got to be about 280-300 metres to the top there, hasn't it?

-Just about, yes.

And you've done this in an insane time?

Yeah. Yeah, I'd like to see if you guys could beat that time today?

-What's your best time?

-Er, about 13.5 minutes so far.

You are the smuggest person I have ever met in my life.

I swear to God, we're gonna take you round the back and beat you up!

-Yeah.

-Oh, God, shall we do this, Steve?

I guess so, yeah.

-Any tips?

-Erm, just...

-Tell me, not him!

-Just don't stop.

I think they're possibly under starter's orders.

On your marks... Get set...

Go!

I can see...Dan loping across just in front of the helipad...

Steve's taken an early lead,

but not going too hard off the start might be Dan's big idea.

It's all part of the plan,

all part of the plan.

Who's gonna win? Well, Dan's got unfeasibly long legs,

but a long stride on that slope may not do him any good at all.

Steve, wildly competitive, exercises like a fiend, but shorter.

Who knows?

The chimney run is 700 metres long, and the last 200 are almost vertical.

Ohhh, but they're going to be in agony...

..just about now...

HE GASPS

'It's so steep, resorting to all fours is the only way to get up here.'

C'mon, Steve!

SHE LAUGHS

Wow!

Where's Dan?

You don't care, do you?

SHE LAUGHS

C'mon, mate...

THEY GASP

C'mon, mate, you're nearly there!

HE GASPS HEAVILY

THEY GASP

Right, the official times on the watch...

'12.50 for Steve,

-'and an impressive 13.12 for Dan.'

-Ah, nice!

-Thank you, Sam.

-Well done to the both of them.

That is thoroughly respectable,

and I, for one...

-I'm proud of you both.

-Thank you!

But I don't want to get much closer to you until you've had a shower.

The feeling's mutual!

Next time on Britain's Lost World,

Steve takes on the ultimate St Kildan challenge...

..Dan looks for human life beneath the waves...

..and I finally learn where our St Kildan mail boat ended up.

Ooh, it's ringing...

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