0:00:10 > 0:00:12This is Coast.
0:00:40 > 0:00:43In the British Isles, we're familiar with wet weather
0:00:43 > 0:00:46blown in from the wild seas.
0:00:49 > 0:00:51One benefit of a temperate climate
0:00:51 > 0:00:53is our wonderful labyrinth of rivers.
0:00:55 > 0:00:58Giant waterways powered by rain,
0:00:58 > 0:01:01that all run to the coast.
0:01:02 > 0:01:06As rivers and seas collide great estuaries emerge.
0:01:13 > 0:01:16Making our mark on these colossal watery spaces
0:01:16 > 0:01:19has taken centuries of struggle.
0:01:19 > 0:01:22That's left a wealth of extraordinary stories
0:01:22 > 0:01:25waiting to be discovered along our estuaries.
0:01:27 > 0:01:30We're braving three of our greatest,
0:01:30 > 0:01:35the Firth of Forth, the Thames and the mighty Severn.
0:01:35 > 0:01:38We're here to explore what becomes of the coast
0:01:38 > 0:01:41when rivers and seas collide.
0:01:46 > 0:01:49I'm starting my estuary odyssey
0:01:49 > 0:01:52a pebble's throw from Edinburgh, on the Firth of Forth.
0:01:55 > 0:01:57The scale of this seaway is staggering,
0:01:57 > 0:02:00it's impossible to take the whole thing in.
0:02:03 > 0:02:07What I could really do with is something tall to climb up
0:02:07 > 0:02:08so I can get a bird's-eye view.
0:02:14 > 0:02:18Only the engineering marvel of the Forth rail bridge
0:02:18 > 0:02:22does justice to the sheer spectacle of the estuary.
0:02:23 > 0:02:25As we're coming up here
0:02:25 > 0:02:27you can see the rivets on this bridge that hold it together.
0:02:27 > 0:02:316.5 million rivets, and every one of them has been painted by hand.
0:02:38 > 0:02:41This is it. This is it, Nick. Here we are on top of the Forth Bridge.
0:02:47 > 0:02:49FOGHORN SOUNDS
0:02:53 > 0:02:56Up here, right in the middle of the Firth of Forth
0:02:56 > 0:02:58you can get a real sense
0:02:58 > 0:03:01of the huge scale of this estuary.
0:03:01 > 0:03:04I can see the Pentland Hills right over there,
0:03:04 > 0:03:08there's the dark volcanic bump of Arthur's Seat
0:03:08 > 0:03:12rising above the white buildings of Edinburgh.
0:03:12 > 0:03:16Looking west, I can see all the way out to the open sea - the North Sea.
0:03:18 > 0:03:21And looking inland, in this direction, there's even more.
0:03:23 > 0:03:26Here's the Forth Road Bridge
0:03:26 > 0:03:28arcing over the water in front of me,
0:03:28 > 0:03:31behind it Rosyth naval base.
0:03:31 > 0:03:33In the far distance
0:03:33 > 0:03:36I can just make out Grangemouth power station
0:03:36 > 0:03:37oozing smoke into the sky.
0:03:41 > 0:03:46This estuary is so huge that even from this incredible vantage point,
0:03:46 > 0:03:49inland it just fades into invisibility.
0:03:49 > 0:03:52The only way of actually getting a true sense of its size
0:03:52 > 0:03:55is by looking at a map.
0:03:58 > 0:04:00This is the mouth of the estuary
0:04:00 > 0:04:04marked by this little island, the Isle of May, here.
0:04:04 > 0:04:08In the other direction, 60 miles inland,
0:04:08 > 0:04:11the water gets less and less salty, gets fresher and fresher,
0:04:11 > 0:04:14until you reach Stirling here,
0:04:14 > 0:04:16where this estuary is born.
0:04:20 > 0:04:22Starting at its birthplace,
0:04:22 > 0:04:24I'm flying the length of the waterway.
0:04:26 > 0:04:28Will the change in wildlife
0:04:28 > 0:04:32help pinpoint the elusive spot where river becomes sea?
0:04:32 > 0:04:36My guide is marine ecologist Stuart Clough.
0:04:38 > 0:04:40And as we pass over Stirling,
0:04:40 > 0:04:42the river's very beautiful seen from above,
0:04:42 > 0:04:44it's like a huge coiled rope.
0:04:44 > 0:04:47You're in classic lower river territory here, erm,
0:04:47 > 0:04:49lower freshwater river.
0:04:49 > 0:04:52The place where the tide just starts to have its effect.
0:04:52 > 0:04:56And even now the mud banks are starting to appear on the side.
0:04:56 > 0:04:59And in those, you've got all kinds of worms and shellfish
0:04:59 > 0:05:02that live within those sediments, and they become food for birds.
0:05:02 > 0:05:04It's a fantastic environment.
0:05:04 > 0:05:09Is it possible to identify the point at which this river, the Forth,
0:05:09 > 0:05:13ceases to be a river and begins to be sea?
0:05:13 > 0:05:15From a biologist's perspective, it's a continuum -
0:05:15 > 0:05:17it changes all the time.
0:05:17 > 0:05:19On the one hand it's a no-man's-land
0:05:19 > 0:05:22and, on the other hand, it's a diverse and rich place
0:05:22 > 0:05:23with masses of life.
0:05:27 > 0:05:30Life is rich where rivers and seas meet.
0:05:33 > 0:05:37And where we flock, so does the wildlife.
0:05:39 > 0:05:42As we move into saltwater,
0:05:42 > 0:05:46the big hitters start to surface -
0:05:46 > 0:05:48dolphins, seals,
0:05:48 > 0:05:51and even whales have all been spotted here.
0:05:53 > 0:05:56We're now over the sunlit seaside, aren't we, Stuart?
0:05:56 > 0:05:59It's completely changed.
0:05:59 > 0:06:02Absolutely, yeah. We're right out in the outer estuary now.
0:06:02 > 0:06:05The freshwater influence is a long way behind us,
0:06:05 > 0:06:06the beaches are sandy.
0:06:06 > 0:06:08If we were down at sea level now
0:06:08 > 0:06:10what kind of birds and so on would we be looking at?
0:06:10 > 0:06:13Auks - like razorbills and guillemots and puffins.
0:06:13 > 0:06:16You've got fulmar, you'll have kittiwakes, you'll have gannets -
0:06:16 > 0:06:19real marine species that you'd never find
0:06:19 > 0:06:21in the freshwater parts of the estuary.
0:06:25 > 0:06:28At the edge of the estuary,
0:06:28 > 0:06:31we get a box-office view of the gannets of Bass Rock.
0:06:33 > 0:06:36This swirling mass makes the most of food from the sea
0:06:36 > 0:06:38and shelter from the land.
0:06:40 > 0:06:42Where are we now?
0:06:42 > 0:06:44We're just adjacent to the Isle of May -
0:06:44 > 0:06:46very much the outer limit of the estuary.
0:06:46 > 0:06:52We've flown the whole way from the freshwater of a river
0:06:52 > 0:06:55to the saltwater of the open sea.
0:06:55 > 0:06:58Over an extraordinary diversity of habitats
0:06:58 > 0:07:03both human and natural - estuaries are worlds of their own.
0:07:10 > 0:07:1220 million of us,
0:07:12 > 0:07:17one third of the UK's population, live on an estuary.
0:07:19 > 0:07:23Their flat shorelines are perfect for building,
0:07:23 > 0:07:28so each of these coastal highways comes with its own gatekeeper.
0:07:32 > 0:07:35Great cities surge up
0:07:35 > 0:07:39where mighty rivers plunge into the sea.
0:07:39 > 0:07:42It's fitting that the country's capital
0:07:42 > 0:07:45crowns the most hard-working waterway of all -
0:07:45 > 0:07:48the titanic Thames.
0:07:50 > 0:07:53For centuries, Londoners have swallowed up the benefits
0:07:53 > 0:07:55the estuary brings in.
0:07:57 > 0:07:59The sea brought riches from abroad,
0:07:59 > 0:08:03and the river supplies two thirds of the city's drinking water.
0:08:05 > 0:08:10But the Victorians found a new job for old Father Thames -
0:08:10 > 0:08:13doing their dirty work.
0:08:16 > 0:08:22Tessa's getting to grips with a grubby tale of triumph and tragedy.
0:08:23 > 0:08:27The power of the tide gave an eminent Victorian engineer
0:08:27 > 0:08:30an extraordinary idea -
0:08:30 > 0:08:35turn the Thames into a giant self-flushing loo.
0:08:36 > 0:08:42The tidal range of the river is huge - around eight metres.
0:08:42 > 0:08:48This powerful ebb and flow gave rise to an ingenious sewer plan -
0:08:48 > 0:08:52release excrement as the tide turns,
0:08:52 > 0:08:54and let the outgoing flow
0:08:54 > 0:08:58flush London's waste way out to sea.
0:08:59 > 0:09:01The city's relationship with the sea
0:09:01 > 0:09:04spawned a sewer system that was the envy of the world.
0:09:04 > 0:09:07Opened in 1865 by the Prince of Wales
0:09:07 > 0:09:09this subterranean labyrinth
0:09:09 > 0:09:13elevated its mastermind, Joseph Bazalgette,
0:09:13 > 0:09:16to become a hero of the Victorian age.
0:09:20 > 0:09:24Bazalgette's master plan demanded a warren of waste pipes,
0:09:24 > 0:09:28a network over 1,000 miles long
0:09:28 > 0:09:31to carry the capital's raw sewage out to the Thames.
0:09:31 > 0:09:34It took six years to build,
0:09:34 > 0:09:38constructed so well it still forms the backbone
0:09:38 > 0:09:41of London's sewer complex.
0:09:41 > 0:09:45Over 300 million bricks placed so precisely
0:09:45 > 0:09:47they form watertight tunnels.
0:09:50 > 0:09:53You know how to treat a girl, don't you, Rob?
0:09:53 > 0:09:56I do, I take them only to the best spots.
0:09:56 > 0:09:58Impressive as this labyrinth is,
0:09:58 > 0:10:00it's only the means to a watery end.
0:10:00 > 0:10:04The city's sewage still needed sweeping out to sea,
0:10:04 > 0:10:06so it was piped towards the coast
0:10:06 > 0:10:09to pass the problem onto the tide.
0:10:09 > 0:10:11The muck flowed downstream
0:10:11 > 0:10:15to arrive at the final triumph of the entire system,
0:10:15 > 0:10:19the pumping station at Crossness.
0:10:27 > 0:10:31This is staggering!
0:10:31 > 0:10:32It's like some sort of ballroom.
0:10:39 > 0:10:42It's a real indication of the level of pride
0:10:42 > 0:10:46they took in their work, the beauty is just breathtaking.
0:10:46 > 0:10:47And these huge pumps
0:10:47 > 0:10:52are even named after members of the royal family.
0:10:55 > 0:11:00The pumping stations were the final stage of Bazalgette's grand plan -
0:11:00 > 0:11:03they pushed the sewage up into huge reservoirs,
0:11:03 > 0:11:06to be stored until the tide began to turn.
0:11:12 > 0:11:13When the tide started to ebb,
0:11:13 > 0:11:17they released the sewage into the Thames just there.
0:11:17 > 0:11:19They relied on the surge of seawater
0:11:19 > 0:11:23to whisk Londoners' muck out of sight and out of mind.
0:11:23 > 0:11:27This was Joseph Bazalgette's big tidal flush -
0:11:27 > 0:11:32his plan to turn the Thames into one gigantic toilet bowl was complete.
0:11:34 > 0:11:38Bazalgette was heralded as the city's saviour.
0:11:38 > 0:11:42But is there a skeleton lurking in London's water closet?
0:11:43 > 0:11:46Life may have been rosy for those in central London,
0:11:46 > 0:11:51but it didn't smell so sweet for those living downstream.
0:11:54 > 0:12:00Like a real-life toilet, the Thames is full of U-bends.
0:12:00 > 0:12:04The waste wasn't clearing as fast as Bazalgette had imagined,
0:12:04 > 0:12:08and the consequences turned out to be devastating.
0:12:09 > 0:12:12It's the 3rd of September 1878,
0:12:12 > 0:12:16the pleasure steamer The Princess Alice
0:12:16 > 0:12:20is on its way back to London crammed with passengers.
0:12:20 > 0:12:22The day-trippers had been enjoying fresh air
0:12:22 > 0:12:24at the mouth of the estuary
0:12:24 > 0:12:27but, returning to the city, near the sewage outlet,
0:12:27 > 0:12:30the pleasure steamer was struck by disaster.
0:12:34 > 0:12:36It collides with another boat.
0:12:36 > 0:12:41Hundreds are flung into the river, many will be drowned.
0:12:41 > 0:12:43But it's even worse than that.
0:12:46 > 0:12:49Revealing the gruesome fate of those floundering in the estuary
0:12:49 > 0:12:51is local historian Joz Joslin.
0:12:53 > 0:12:57So the vessel's upended, and hundreds of people are in the water.
0:12:57 > 0:13:00Yes. And lots of them are women and children,
0:13:00 > 0:13:02and they're screaming,
0:13:02 > 0:13:05and unfortunately it's not water that they're in,
0:13:05 > 0:13:08they're actually in sewage, so there was no oxygen.
0:13:08 > 0:13:12A lot of them died because there was no air to breathe.
0:13:12 > 0:13:15So they're either being suffocated or drowning.
0:13:15 > 0:13:17Or poisoned.
0:13:17 > 0:13:19How revolting. And the majority died?
0:13:19 > 0:13:21Yes, the majority died.
0:13:21 > 0:13:23They said that every street in the east end of London
0:13:23 > 0:13:24had lost somebody,
0:13:24 > 0:13:27because it was their Sunday school outings
0:13:27 > 0:13:29that were on board the vessel.
0:13:29 > 0:13:32The pleasure boat sank close to the sewage works,
0:13:32 > 0:13:37and the timing could not have been worse.
0:13:37 > 0:13:41The Beckton sewage outlet pipe carrying all of North London's waste
0:13:41 > 0:13:45had just discharged its stinking load into the river.
0:13:47 > 0:13:52Over 600 people choked to death in a toxic soup of human filth.
0:13:58 > 0:14:00After the tragedy,
0:14:00 > 0:14:05Bazalgette's sewage system came under the spotlight.
0:14:05 > 0:14:08Members of the local historical society
0:14:08 > 0:14:11read the words of their forefathers.
0:14:11 > 0:14:14"There had been an accumulation of black, greasy,
0:14:14 > 0:14:16"filth along the shore.
0:14:16 > 0:14:19"The filth settles on the steps as the tide goes down."
0:14:19 > 0:14:22"The river in hot weather is very bad.
0:14:22 > 0:14:25"In some places it smells so bad you cannot stand it."
0:14:25 > 0:14:29A commission of inquiry delivered a damning indictment,
0:14:29 > 0:14:33concluding "it is neither necessary or justifiable
0:14:33 > 0:14:37"to discharge sewage in its crude state
0:14:37 > 0:14:39"into any parts of the Thames".
0:14:39 > 0:14:43The Pall Mall Gazette took Bazalgette to task,
0:14:43 > 0:14:45stating "the natural man in him,
0:14:45 > 0:14:49"puts off the evil day of having to admit failure."
0:14:50 > 0:14:54Luckily for Bazalgette, the muck didn't stick,
0:14:54 > 0:14:59but London did pull the plug on his big tidal flush.
0:14:59 > 0:15:03In 1887, a new system started.
0:15:03 > 0:15:07Now the solid human waste was pumped into vessels like this.
0:15:07 > 0:15:12The excrement was shipped out to the open sea and dumped.
0:15:12 > 0:15:16They were known locally as Bovril boats, amongst other things.
0:15:16 > 0:15:20We used to call them... Well, never mind what we used to call them!
0:15:20 > 0:15:23What did you call them? No, I'm not saying.
0:15:23 > 0:15:26They used to come and moor - they had moorings for them -
0:15:26 > 0:15:28and they would take the residue of it.
0:15:28 > 0:15:30Cos all the fluids were taken off,
0:15:30 > 0:15:32so it was almost solid the stuff
0:15:32 > 0:15:35that they took out - human detritus -
0:15:35 > 0:15:38so that it wasn't into the river.
0:15:38 > 0:15:42Sewage carrying ships didn't just do the dirty work of London -
0:15:42 > 0:15:45they were once a common sight on our estuaries,
0:15:45 > 0:15:50cleaning up Glasgow, Belfast and other coastal cities.
0:15:53 > 0:15:58London's Bovril boats were finally pensioned off in 1998.
0:16:01 > 0:16:04Bazalgette's tunnels still bring raw sewage here
0:16:04 > 0:16:07to the Crossness Works,
0:16:07 > 0:16:10but now the solid matter's burnt off to make electricity.
0:16:13 > 0:16:15The liquid sewage is treated -
0:16:15 > 0:16:17it goes from this...
0:16:17 > 0:16:19to this.
0:16:19 > 0:16:21And the cleaned-up fluid?
0:16:21 > 0:16:23It still gets the big tidal heave-ho,
0:16:23 > 0:16:27and is discharged into the Thames, where the river and the sea collide.
0:16:37 > 0:16:40The Severn estuary used to pose a fearsome challenge
0:16:40 > 0:16:43on any journey between England and Wales.
0:16:45 > 0:16:50The two countries were divided by this massive tear in our coastline.
0:16:51 > 0:16:56Avoiding it meant a diversion deep inland.
0:16:56 > 0:17:01Even so, only hardy travellers would brave the deadly waters.
0:17:08 > 0:17:12Today, a concrete solution spans this vast channel.
0:17:14 > 0:17:18But conquering the Severn was a bold venture fraught with peril,
0:17:18 > 0:17:21as Mark is about to discover.
0:17:23 > 0:17:26Dashing over the estuary from Wales to England,
0:17:26 > 0:17:32commuters take the elegant crossings their lives depend on for granted.
0:17:34 > 0:17:37But imagine a world before this bridge was possible.
0:17:37 > 0:17:40A world without steel cables,
0:17:40 > 0:17:42without reinforced concrete,
0:17:42 > 0:17:46when the sea reigned supreme.
0:17:46 > 0:17:50That was a challenge faced by the Victorians
0:17:50 > 0:17:52to cross the River Severn.
0:17:56 > 0:18:01The formidable collision of river and sea facing the early engineers
0:18:01 > 0:18:03can still be experienced.
0:18:05 > 0:18:08It's one of the most dangerous seaways in the world,
0:18:08 > 0:18:10and I'm just a little bit excited.
0:18:12 > 0:18:15The Severn Area Rescue Association
0:18:15 > 0:18:19is going to pit me against the ebb tide.
0:18:21 > 0:18:23Cast off!
0:18:23 > 0:18:25The power of the tide here is just extraordinary!
0:18:32 > 0:18:36As the tide goes out it's like a maelstrom.
0:18:36 > 0:18:40The waters were an immense challenge
0:18:40 > 0:18:44but, by the 1840s, crossing the river by boat was old hat.
0:18:48 > 0:18:52An irresistible new force was spreading across Britain -
0:18:52 > 0:18:53the railways.
0:18:53 > 0:18:56Come hell or high water,
0:18:56 > 0:18:59estuaries weren't going to stand in the way of progress.
0:19:03 > 0:19:06The great Victorian engineer Isambard Kingdom Brunel
0:19:06 > 0:19:08is a hero of mine -
0:19:08 > 0:19:11he'd already managed to cross the Avon gorge
0:19:11 > 0:19:13with a mighty suspension bridge.
0:19:13 > 0:19:17When his railway came to Bristol, he wanted to cross into South Wales,
0:19:17 > 0:19:20and planned an even bigger suspension bridge.
0:19:20 > 0:19:22Here are the preliminary sketches.
0:19:23 > 0:19:25The biggest problem
0:19:25 > 0:19:29was the sheer scale of the span that Brunel required -
0:19:29 > 0:19:31over 1,000 feet.
0:19:33 > 0:19:36He left a little note in his notebook,
0:19:36 > 0:19:41which says "is 1,100ft practicable?"
0:19:43 > 0:19:46Brunel's bridge was never built,
0:19:46 > 0:19:51but if taking trains over the water defeated the best brain of the age,
0:19:51 > 0:19:53how about going underneath?
0:19:56 > 0:19:59A tunnel - was that the answer?
0:19:59 > 0:20:03Digging deep to create a railway under the water -
0:20:03 > 0:20:08this was very bold, big thinking.
0:20:08 > 0:20:12This is one of the original drawings of the tunnel from around 1887,
0:20:12 > 0:20:16and you can see how the track comes down
0:20:16 > 0:20:20underneath the deepest part of the Bristol channel here, in The Shoots,
0:20:20 > 0:20:23and gradually up to the Welsh side.
0:20:23 > 0:20:28So what we've got here is around seven miles of railway track.
0:20:29 > 0:20:33That passage under the estuary is now a vital link
0:20:33 > 0:20:36between England and Wales.
0:20:36 > 0:20:40Carrying over 250 trains a day.
0:20:41 > 0:20:45Passengers are oblivious to a catastrophe
0:20:45 > 0:20:50that nearly sank the tunnel before the first train ran,
0:20:50 > 0:20:53and is a problem that still lurks below.
0:20:58 > 0:20:59So, here we go.
0:20:59 > 0:21:04I've been granted access to a shadowy water world
0:21:04 > 0:21:07few get to see.
0:21:07 > 0:21:09It's great - we're just coming into the cutting,
0:21:09 > 0:21:14the portal's ahead, and we're about to go under the sea.
0:21:18 > 0:21:21Ah! Wahey!
0:21:21 > 0:21:22Isn't that fantastic?!
0:21:24 > 0:21:27We're heading for the deepest point in the tunnel.
0:21:30 > 0:21:32Just 50ft above us
0:21:32 > 0:21:36millions of gallons of water are swirling around -
0:21:36 > 0:21:40the River Severn and the sea are in full flow.
0:21:40 > 0:21:44Keeping the water out here is hard enough,
0:21:44 > 0:21:46but can you imagine if there was a flood down here?
0:21:49 > 0:21:52With an estuary hanging over their heads,
0:21:52 > 0:21:55engineers knew there'd be seepage of seawater,
0:21:55 > 0:22:00but it was freshwater that nearly drowned the project.
0:22:02 > 0:22:06Nobody expected this -
0:22:06 > 0:22:09a raging torrent!
0:22:09 > 0:22:12They'd broken through to an underground spring.
0:22:13 > 0:22:18In October 1879, water began to pour into the tunnel.
0:22:20 > 0:22:22The workers fled for their lives.
0:22:24 > 0:22:29The disaster struck when a shaft dug on the Welsh coast
0:22:29 > 0:22:33cut into an underground river deep below the surface.
0:22:36 > 0:22:40For four years, the engineers made desperate attempts
0:22:40 > 0:22:43to block the freshwater spring,
0:22:43 > 0:22:46but every effort proved futile.
0:22:48 > 0:22:53And it's been flooding in at this alarming rate ever since.
0:22:53 > 0:22:57If they couldn't stop the spring water, they'd have to live with it.
0:23:01 > 0:23:02The only solution were pumps,
0:23:02 > 0:23:08massive ones like this that pump the water out as fast as it comes in,
0:23:08 > 0:23:09right up to the surface.
0:23:12 > 0:23:16Leighton Jenkins helps keep the tracks dry today.
0:23:16 > 0:23:19So what would happen if the pumps actually failed?
0:23:19 > 0:23:21Every second counts,
0:23:21 > 0:23:24as soon as the pumps stop we'd have to inform the control
0:23:24 > 0:23:27within 10 minutes to shut the tunnel itself,
0:23:27 > 0:23:30and within 20 minutes we've got water coming up through the tracks,
0:23:30 > 0:23:32so every second absolutely counts.
0:23:32 > 0:23:34But have they ever failed?
0:23:34 > 0:23:38No, not as far as I know, no. Not while I'm on a shift anyway.
0:23:40 > 0:23:43The railways had proved irresistible.
0:23:43 > 0:23:47With rival Victorian companies vying for routes,
0:23:47 > 0:23:52by the time it was finished the tunnel already had a competitor.
0:23:56 > 0:24:02In 1879, trains had started to roll over the estuary,
0:24:02 > 0:24:04but the bridge's sturdy uprights -
0:24:04 > 0:24:07always an obstacle to shipping -
0:24:07 > 0:24:09would ultimately prove its downfall.
0:24:12 > 0:24:14Do you see, that's a tower
0:24:14 > 0:24:20where the railway bridge once crossed the Severn Estuary.
0:24:20 > 0:24:22I've got a photograph
0:24:22 > 0:24:26that shows the stanchions marching across the river -
0:24:26 > 0:24:28now totally destroyed.
0:24:31 > 0:24:35The raging waters where river and sea smash together
0:24:35 > 0:24:39would deliver a fatal blow to the rail bridge.
0:24:43 > 0:24:48In October 1960, the Arkendale, carrying oil,
0:24:48 > 0:24:51and the Wastdale, laden with petrol,
0:24:51 > 0:24:55were heading for combustible collision.
0:24:55 > 0:25:00The Arkendale was carried in by the surging tide.
0:25:00 > 0:25:05That powerful current would drive it into the Wastdale
0:25:05 > 0:25:09on a foggy night at Sharpness Docks.
0:25:09 > 0:25:11As Alan Hayward knows.
0:25:13 > 0:25:16They were coming upriver intending to come into the docks here,
0:25:16 > 0:25:19but they were accidentally swept past.
0:25:19 > 0:25:23And then they collided and became, in effect, stuck together.
0:25:24 > 0:25:27Disabled ships in thick fog,
0:25:27 > 0:25:31carrying 600 tonnes of inflammable cargo
0:25:31 > 0:25:33at the mercy of a swirling sea,
0:25:33 > 0:25:36propelled them to disaster.
0:25:38 > 0:25:41They were desperate to separate from each other,
0:25:41 > 0:25:43fighting by steering in different directions,
0:25:43 > 0:25:45but it just didn't work.
0:25:45 > 0:25:47And they only had about four minutes
0:25:47 > 0:25:49before they would reach the railway bridge.
0:25:51 > 0:25:55The rail bridge across the Severn loomed out of the fog,
0:25:55 > 0:26:00a collision with the ships carrying oil and petrol was now inevitable.
0:26:07 > 0:26:08A lot of sparks would have been created
0:26:08 > 0:26:11which ignited the petrol in one of the vessels.
0:26:14 > 0:26:16The fuel, of course, spilt out over the river,
0:26:16 > 0:26:18so the whole river became a mass of flame.
0:26:22 > 0:26:26First mate Percy Simmonds was aboard one of the tankers.
0:26:26 > 0:26:29His son Chris was 13 at the time.
0:26:29 > 0:26:32I try to imagine that night and what he was going through,
0:26:32 > 0:26:35and it must have been just terrible with the flames and everything.
0:26:35 > 0:26:39I'm just sure he was determined to make it across this river somehow
0:26:39 > 0:26:43and make it back to us.
0:26:43 > 0:26:47Daylight and a low tide revealed wrecks of the fuel tankers
0:26:47 > 0:26:51smouldering on a sandbank.
0:26:51 > 0:26:54Soon the first body was found.
0:26:54 > 0:26:56They identified the body there,
0:26:56 > 0:27:02and they, you know, let Mum know that, yeah, it was definitely Perce.
0:27:02 > 0:27:06Chris's father Percy died along with four others
0:27:06 > 0:27:08on that terrible evening.
0:27:08 > 0:27:14The damaged bridge was too expensive to repair, it was demolished.
0:27:14 > 0:27:17But each day, when the tide recedes,
0:27:17 > 0:27:20scars of tragedy are revealed.
0:27:20 > 0:27:22Out there, of course, are two hulks,
0:27:22 > 0:27:27buried now in the sands that have been washed over by countless tides.
0:27:27 > 0:27:30But they're still there. They're there as monuments.
0:27:30 > 0:27:32They're here as a reminder to all of us.
0:27:35 > 0:27:37It's immensely humbling
0:27:37 > 0:27:43to be next to such a vast body of brooding water.
0:27:43 > 0:27:47Even on a calm day like this
0:27:47 > 0:27:49one can feel the power
0:27:49 > 0:27:52where rivers and sea collide.
0:28:02 > 0:28:06Surging waters urge us on to fresh endeavours.
0:28:08 > 0:28:11And we're not alone in finding creature comforts
0:28:11 > 0:28:14around the fringes of our great seaways.
0:28:16 > 0:28:18The tide brings in the bounty
0:28:18 > 0:28:21that makes our estuaries brim with vitality.
0:28:30 > 0:28:35Safe havens that offer boundless prospects.
0:28:35 > 0:28:40Where rivers collide with the sea our coast comes alive
0:28:40 > 0:28:42and opportunity awaits.
0:29:11 > 0:29:15If it ever came to pass that Mr Corbyn were the Prime Minister,
0:29:15 > 0:29:18this country would be a basket case.
0:29:18 > 0:29:21Well, I think we're a basket case now. Have you seen Southern Rail?
0:29:21 > 0:29:23Have you seen the National Health Service?
0:29:23 > 0:29:27And we'll be more of a basket case once she triggers Article 50.