Episode 2 Dive WWII: Our Secret History

Londonderry is famous for a remarkable siege.

But there's an extraordinary time in the city's more recent past

that's been forgotten.

The years when Derry was at the centre of World War II's

longest and most decisive battle.

The Battle of the Atlantic.

To reveal this story, we begin not in the city,

but on the waters off its coast.

Out there, on the horizon, hidden deep beneath the waves,

lie hundreds of forgotten shipwrecks.

Together, they tell the story of an extraordinary conflict.

It lasted nearly six years.

100,000 men died and 4,000 ships were sunk.

Wrecks from the battles still litter the seabed here,

lost, forgotten and out of reach, until now.

One underwater explorer has compiled a unique map.

It charts the lost wrecks of the Battle of the Atlantic.

Now he and a team of expert divers are going in search of them,

to uncover the lost stories of the battle.

All hatches are closed.

There's an open locker with live ammunition in it.

What they discover, will restore Derry's lost place in the history

of World War II.

The Battle of the Atlantic could not have been won

if the bases on the Foyle had not been available to the Allies.

The residents of Derry had been on the front line

so this is an opportunity for them to see the U-boat gotten rid of.

And over 70 years later, the generation who witnessed

first-hand this extraordinary time in Derry, share their experiences.

He was so badly injured. His body was covered in splinters.

To me, this was part of the U-boat coming alive, you know?

The dancing and the courting and coming home with boys.

I feel like I want to take him out of the screen and give him a hug.

All you think about is what the people back home will think

when they know I'm dead.

In this series, we'll dive back through history to uncover

how one city helped forge victory in the Battle of the Atlantic.

Late 1941.

Derry had spent two years on the battle's front line

and had seen the Germans hammer Allied shipping.

In just three months that year,

their U-boats sank more than 280 ships off the Northern Irish coast.

But the Allies were determined to fight back.

Warships crammed the Foyle and Derry filled with 30,000

British, Canadian and American military personnel.

The residents of Derry found themselves living

in extraordinary times.

The U-boats had brought the battle right to their doorstep.

The people of this city came face-to-face with the tragedy

and reality of World War II, but they dug deep and they got stuck in.

Northern Ireland's war effort brought full employment to Derry,

as the demand for exports increased.

For the women, this meant new jobs making ammunition,

linen and uniforms.

They were in the factory and they all sort of went down for a smoke.

It was all, "Where did you go last night?"

And, "Who did you come home with?"

Every morning, we had music while you worked, so life was good.

There may have been hardships, but Derry's men and women

met these with cheery resourcefulness.

You couldn't get sugar, sweets, cigarettes were very scarce.

Rationing was pretty strict but Donegal wasn't that far away.

Oh, smuggling was big. Especially across the border.

My mother and them had it down to a fine art.

They got the train in Jones Street and they had bags under

their skirts and they did quite a lot of smuggling, I'm telling you.

And the presence of thousands of international troops

in the city, brought its own advantages.

American soldiers, they were terribly kind

and they used to wander around and talk to the children

and give the children sweets and maybe hand out cigarettes and things.

An American used to appear every so often

when the ship was in and one day, he brought us a banana.

They were absolutely... You never knew what they were.

But we auctioned it

and got £3 for it in the middle of the war.

Between all that and the dancing and the courting

and come home with boys, and if they got too fresh

you took to your heels and away you went

because you were afraid of your mother.

I must say, I thoroughly enjoyed the war.

There may have been good times in Derry, but there was no

escaping the grim reality of a city and a world at war.

I remember going to dances at the Strand picture house

on a Saturday night with the girls out of the office

and Julie Glover, whose father was a chemist in William Street.

He went away to the RAF.

And he was shot down and...

He would only have been about 19, I suppose.

In military campaigns around the world,

young men were losing their lives.

But nowhere more so than in the Battle of the Atlantic,

where 100,000 were killed. At its crux, were military supplies.

Every week, huge convoys of cargo ships loaded with weaponry,

oil and food, left the United States and Canada.

Without them, the Allied war effort in Europe would grind to a halt.

So Germany sent its U-boat fleet to sink

the convoys before they reached their destinations.

Underwater explorer, Ian Lawler, and his team of expert divers,

are searching for lost wrecks of the battle.

I can see the U-boat.

They've already found the remains of a Corvette,

a warship still loaded with ammunition.

It is much more of a jigsaw puzzle than I expected.

World naval experts, Dr Randy Papadopoulos

and Dr Axel Niestle, are on hand to unlock the secrets of the wrecks.

The acoustic homing torpedo would have targeted the loud engines

of the Corvette and essentially would've blown her stern off.

Dozens of Corvettes like this one moored up in Derry.

Their job, to escort the convoys across the Atlantic and protect them

from the U-boats which were deadly,

as the team revealed

when they discovered the wrecks of two German submarines.

First, U-1003.

Very capable fighting machines and very dangerous to the Allies.

Then, U-155,

a notorious sub that claimed the lives of nearly 1,000 men.

During the war, all of these things are forgotten about.

They're just incidental.

But it's generally the divers that start to make the discoveries

and try and shed light on what happened.

When you find what you're looking for,

that's what makes it all worthwhile.

The wrecks also revealed Derry's role in the conflict.

As Britain's most westerly port, it was essential,

a key naval base for the armed escorts.

It was the battle's frontline.

And the city's hospitals were the first chance for the wounded

to get life-saving treatment.

Lexie Edgar was a nurse who volunteered

with the St John's Ambulance.

He met the battle scarred convoys at Lough Foyle

and rushed their injured crews to hospital.

We went down to where the heavy cruiser

was protecting against submarines

and we took the injured people off into smaller boats

and brought them up to the Foyle.

Any injuries we could help out with, we gave them... We dressed them up.

Where there were more severely injured,

we sent them off to city and county.

I remember having to travel down and help a chap back.

He was so badly injured and he was strapped from head to toe.

There wasn't a lot left of him.

His body, as I say, was covered in splinters.

Lexie and his colleagues kept a logbook of the real human cost

of the Battle of the Atlantic.

On the face of it, this is a fairly simple record.

Three columns, the date, the name of the ship

and the number of passengers and crew that Lexie actually treated

that came off it.

And it does begin to tell you a fairly detailed story

as to the growing human cost

and human tragedy that was unfolding across the Atlantic.

Broadly speaking, each page covers about five or six months

and as it goes through the war, the numbers tell the story.

Page one, he's treated 432 individuals.

Here, 470.

555, moving into 1943, 490.

When you add it all together,

you get a total of 3,401 recorded throughout the war.

And on the back of this,

is an interesting list of the sorts of cases that Lexie was treating.

Fractured spine, fractured skull, concussion, machine gun wounds,

bullet wounds, burns, of course,

from the burning oil when the ship sank.

And as you would expect, pneumonia.

It's a simple book.

When he wrote this, he never would have expected that this would

become an important historic document.

But it is.

The injured who made it to Derry for treatment were the lucky ones.

100,000 never came home from the battle.

4,000 shipwrecks on the Atlantic seabed remind us of their sacrifice.

Adding to the deadly threat of the U-boats,

was the Atlantic weather.

High winds and violent seas could be deadly.

For underwater explorer, Ian Lawler, and his team of divers,

it's no different.

It's September and they're on the Rosguill Peninsula in north Donegal

hoping to dive a wreck 20 miles offshore.

But today's rough seas could make it too dangerous.

It's not looking good.

You're trying to stagger around in a pair of fins on the back

of a rolling boat with the equivalent of your own body weight

on your back.

The boat is rising and falling a metre to two metres.

That is not an option. It could remove people's heads.

With the best skipper in the world, the best will in the world,

that is very dangerous.

Anybody gets it wrong, through attention or a mistake,

you know, you could be seriously injured.

Skipper, Michael, goes to check conditions one last time

but the weather has got worse.

Even the sheltered waters of the bay are looking choppy.

The day is lost. Gone, nothing.

Deepwater veteran and dive supervisor, Rich Stevenson,

is in charge of safety

and used to assessing the dangers of an expedition.

It's a force of nature, isn't it?

When you can't stand up against something that you can't see.

You've got to pit your wits against the weather

and everything else that you're up against, as well.

You can topple over at a moment's notice.

It's unthinkable to try and dive in these conditions.

It's a reminder of the bravery of the Atlantic crews,

who fought on, whatever the weather.

Very aware of the historical significance

of this area of water and what lies beneath the waves.

You can't even imagine what it must be like to be caught out

in the open ocean in those conditions.

But weather like this and worse,

was a fact of life for men working the Atlantic convoy routes.

The busiest of them all passed through some of the Atlantic's

wildest water, from Newfoundland in Canada to Derry.

Over the war, it introduced thousands of Canadian sailors

to the city.

The Royal Canadian Navy, which had been very small,

just a coastal patrol service at the beginning of the war,

burgeoned to the point, where by 1943,

it's the third largest Navy in the world.

If you look at the 100 plus escort ships that are based on the Foyle,

the vast majority of them are Royal Canadian Navy.

To Canadian sailors, the route was legendary,

known as the Newfie Derry run.

18-year-old Gilbert Davis,

was a stoker on the Canadian escort ship, Merrittonia.

Wherever he went, he brought his camera.

The camera was a small camera. It was a dollar 50 camera.

It was one of the first things he ever bought.

But Gilbert put it to good use, documenting his life

during the Battle of the Atlantic and not just at sea.

Every month he spent time in Derry

and his pictures give a sailor's view of the city.

Approaching the packed docks from the Foyle,

the Allied escort ships moored four deep.

And wartime Bishopsgate.

One place that struck Gilbert,

as a unique spot in Londonderry, was Bishopsgate,

because he understood it was built some time in the 16th century.

That kind of history he hadn't seen over in North America.

Just like all Atlantic crews,

Gilbert arrived in Derry with relief.

It marked the end of another perilous crossing,

not only giving U-boats the slip,

but also surviving the high seas and violent winds of the Atlantic.

The North Atlantic has some of the most unforgiving sea on the planet, really.

That makes it very difficult to have any sort of cargo, or naval operation take place.

Gilbert's photos show the rough seas the Atlantic crews faced.

With the ships rolling in giant swells, Corvettes like Gilbert's

still had to attempt essential tasks like refuelling on the move.

Mountains of water, 30, 40, 60 feet high, and he would be hunkered down

as close as he could to the security of the ship itself.

The Atlantic can be savage.

But wild weather was always preferable to an encounter with a submarine.

There was always the threat of attack from a U-boat.

That itself must have frayed the nerves of many a crewman.

And here we have an example of the aftermath.

Clearly, a tanker has been hit. The ship itself is obscured

in billowing clouds of black, acrid smoke,

and the sea all around it, ablaze.

The tanker had been carrying thousands of tonnes of fuel.

He was on the bow of his ship taking photographs.

He said he had to hold his hand up and guard his face from the heat, it was so intense.

On the horizon is the tanker burning,

and here alongside the hull of his ship, one man,

the only survivor from that attack.

Dwarfed by the tower of smoke and the vast Atlantic,

this man had suffered horrific injuries.

They pulled him aboard the Maritonia,

and as he was pulled from the water by a seaman,

all of the skin from his arm had pulled off because he was so badly burned.

Over 70 years later, the pictures taken by Gilbert Davis

give a remarkable insight into the reality of a sailor's life

fighting the Battle of the Atlantic.

It's one man's record of a campaign

that cost the lives of thousands more.

The dive team are getting ready for their fourth expedition.

They're hoping to uncover the wreck of the U-boat Ian believes

was sunk in the heat of battle just 10 miles from Coleraine.

But on the Rosguill Peninsula, another storm is brewing.

The team are hoping to beat the incoming weather

by heading for Port Stewart and diving from there.

I'm not sure just yet.

This large area of Donegal could give us a bit of shelter.

That would be a lot better. It is a narrow weather window but it's an option.

They plan to use a high-speed rib to race out to the wreck

and back again before the winds hit.

I think it gives us some advantages in certainly speed getting out of there.

-But maybe less home comforts.

-It's quite a stable boat, but you have to hang on.

The team has allowed just 30 minutes to get to the dive site.

And already the winds are picking up.

The high-speed twin engine rib has to battle through the swirl,

while do team do their best to hang on.

With the weather closing in, there isn't a minute to lose.

Once on site, it's straight into the water.

The strong surface swell sweeps the divers from the boat.

Once underwater, they locate the grapple line.

It should lead them 200 feet straight down

directly to the wreck on the seabed.

But the strong current has ripped the grapple off the wreckage,

leaving them searching blindly through the silt.

But then, the beam from a torchlight falls on the rusting hull of a U-boat.

It's over 250 feet long and shows all the hallmarks of a type seven,

the workhorse of the German fleet.

But what intrigues the team is the damage to the hull.

Along its entire length, it's been shattered,

the thick steel ripped open.

This wreck shows all the tell-tale signs of a devastating depth charge attack.

Having had just 20 minutes to gather the evidence they need,

the team now make a controlled two hour assent back to their boat.

As they pile aboard,

Ian can't contain his excitement at what he's seen.

The extensive damage to the U-boat

is the first sign that the enormous efforts in Derry

to win the Battle of the Atlantic were paying off.

In 1941, the Allies sank just 40 U-boats.

In 1943, they sank 270.

But with so many German submarines sunk,

it could be difficult for naval experts

Randy Papadopoulos and Axel Niestle

to identify the wreck Ian and the team have found.

This is a pretty jagged hole here.

And all the plate is just pushed inward.

The pushed in plating that we're seeing here suggests that

something came in from the outside - an explosion, probably.

That's heavy structural damage. This is simply crushed.

-Here we are on the broken end of a snorkel.

-Oh, yeah.

And then the conning tower area is devastated. Absolutely demolished.

This is quite cataclysmic damage.

So that needs a depth charge exploding almost on contact.

-Hundreds of pounds of explosives.

-Yes.

Depth charges were the most common antisubmarine weapon.

Once Allied ships had detected a U-boat,

they would target depth charges over the entire area.

The shockwaves created by the explosions

could tear open the hull of a U-boat lurking beneath the surface.

But you see the thickness of the steel has just been torn, like paper.

-The Royal Navy named it "tin-opener attacks".

-Yes.

That's exactly what has happened obviously to this wreck.

Axel and Randy use the location of the wreck

and the knowledge it was pummelled by depth charges

to search naval records for information to identify it.

At last, they find a match.

From what we know, I think we can surely say that this is 1014.

All what we have found here is consistent with that identification.

Ian and the team's dive has revealed the wreck as U-1014,

a late war Type VII submarine.

It was just 18 days into its first patrol

when a group of British escort ships detected it

eight miles off the coast of Northern Ireland.

They fell into formation and together began to hunt it down.

It's a bit of a ballet of ships, if you will.

All the time moving because the U-boat in addition

is trying to escape and all the ships are trying to keep in contact with it

and put the ordnance where it's needed.

So when they come across a contact, the first thing you do

is start trying to pulverise it with as many depth charges

- or Hedgehog or Squid - whatever weapons they've got available

and make sure you've gotten him,

rather than take a chance and let it get away.

It was finally destroyed while being under the water.

Beneath the surface, the Allied depth charges found their target.

All 48 men inside u1014 were killed.

From 1943, German losses like this were increasingly common,

as the scales began to tip in the Allies' favour.

But it's just one more reminder to the U-boat crews

that are still surviving

that actually their time is going to be limited

because their losses are just simply unsustainable.

As the German Kriegsmarine lost more and more of its crews,

it became harder and harder to replace them with experienced men.

Most of the crew on U-1014 were younger than 22.

These were green soldiers, sent out into a battle against an enemy

which was gaining experience everyday.

This is the Allied navies at the top of the antisubmarine warfare game,

with tactics customised to deal with the inshore threat.

The crew of the British escort ships

had no idea which U-boat they had sunk.

They searched the wreckage that floated to the surface

for anything that might identify their victim.

One everyday item give them a clue.

From the debris picked up after the attack,

there were a pair of underpants picked up with a name on it.

And this name was Moose.

By searching German naval records, Axel has been able to reveal

that Seaman Moose was a 19-year-old engineer mechanic

and that his last recorded patrol was on-board U-1014.

So this is just another support

that the boat being lost in this area is 1014.

Identifying the wreck is another success for Ian and the team -

another name to add to his chart.

But their discovery also marks the war grave of 48 young submariners.

It reveals how the Allies' determination

to keep the convoy routes open,

alongside their growing expertise in hunting submarines,

was now beginning to overpower the German U-boat fleet.

'The Allies may at last have been

'turning the Battle of the Atlantic in their favour,

'but one fatal chink remained - fully effective air cover.

'From 1940, Allied airplanes patrolled parts of the Atlantic,

'flying from coastal bases

in Canada, Iceland and Northern Ireland.'

Whenever a U-boat sees an airplane,

the first temptation for that U-boat commander is to dive.

Once you've forced him below the water,

he's reduced to about four to seven knots.

So it's a brisk walk or a slow trot,

but it's certainly slower than even the slow convoys

which are travelling at about nine or 10 knots.

It means that he cannot pursue the convoy anywhere near as effectively.

His visibility is hindered at the very least.

But, at best, it means the U-boat will have to break off its contact

with the convoy and won't be able to pursue it and hunt it any longer.

But the aeroplanes had limited range

and a vast area of the Atlantic remained unprotected from the air.

This was known as the Mid-Atlantic Gap,

and, for the Germans, the lack of air cover here

made it a prime hunting ground.

It was a gap the Allies needed to close.

So the Royal Navy set about

creating the largest air squadron in the UK,

and they based it here in Derry.

It was a decision that would change the course of the battle.

The plan was for Swordfish biplanes to fly from Maydown

at the edge of the city, land on makeshift aircraft carriers

off the coast, and, for the first time, accompany the convoys

to fly anti-U-boat patrols in the mid-Atlantic.

Eventually, 100 of these planes operated from Derry's new airbase.

We're stepping onto the runways of HMS Shrike.

And if you'd been here 70 years ago,

amid the noise and the bustle and so forth,

you might have been able to see three or four Swordfish biplane bombers

taking off here on the westerly runway, heading out towards Donegal

and then turning out into the Atlantic,

where they would join a small merchant aircraft carrier.

The merchant aircraft carriers, or MAC-ships,

were simply cargo vessels with their superstructure removed

and a few hundred feet of runway welded on instead.

They may have been crude, but with their Swordfish biplanes,

these MAC-ships proved highly effective.

These are very important because they'll provide each convoy

with its own aircraft carrier protection.

Right from the very beginning

of this airfield's existence as a naval base in May of 1943,

we see the Battle of the Atlantic swing in the Allies' favour.

From then on, every convoy is covered by Swordfish

and basically the U-boats daren't operate on the surface any more.

Bob Lee was a telegraphist air gunner with the Swordfish crews

based in Derry. He flew every day in any weather,

standing in the open cockpit at the rear of the Swordfish.

Cold. I don't know why it was always cold.

It seemed to be the worst where we were, you know.

Either in Canada or Northern Ireland. It was always damn cold.

Bob faced danger too, every day.

Just landing a Swordfish on an improvised aircraft carrier

was a hit-and-miss affair.

More than once, he found himself in the drink.

He started to dip down and I thought, "There's something wrong here.

"What's up," you know? And the pilot was pump-pump-pumping.

Something wrong. "Mayday, Mayday, Mayday. This is Swordfish Ellis 246."

Bosch.

And then I heard, "All right, 246, come into land, you're clear.

I thought he'd got the wrong bloody aircraft!

Bob's Swordfish had been given the wrong instructions.

His plane overshot the landing deck of the aircraft carrier

and smashed into the sea.

But, as was the rule, the convoy didn't stop. Bob was left behind.

If the whole group of ships stops,

that whole 40 ship target is a target.

The commodore has no choice but to keep going and let them go.

And a lot of them perished

because they can't have an immediate rescue come to them.

It's a very risky business, not easy to manage

and it cost a lot of people their lives when things go wrong.

Bob was left to drift in the cold Atlantic,

clinging to the wreckage of his biplane as the convoy steamed on.

After about half an hour, along came another Swordfish,

dropped a couple of dinghies which still didn't work

and I thought, "That's it."

They talk about your whole life flashing before you.

But all you think about was

what the people back home will think when they know I'm dead.

That was it.

Bob was eventually rescued by an escort ship,

but he continued to fly, clocking up over 200 hours in the air.

It was a crucial job, and Bob and his fellow crews at Maydown

succeeded in forcing the U-boats to remain submerged.

The availability of those aircraft from mid-1943 onwards in every convoy

meant that there was no part of the ocean that was safe,

as far as the U-boats were concerned,

from the eyes of Allied airmen in the sky above.

The Swordfish were the vital missing piece of the anti-U-boat strategy.

And Maydown became critical to keeping the Mid-Atlantic Gap closed.

The base quickly grew in size, with two British and Dutch

air squadrons operating from here over the war.

One RAF Wren who experienced

how cosmopolitan life at Maydown became was Mary Piper.

It was the women's Royal Naval service,

so that's why she was here, because of the convoys.

She did a lot of the organising of social events and entertainment.

She looked after menus

for different functions and so forth.

I think there was a party

that she was organising

and she invited some of the men from - the officers -

from Dad's 860 Squadron.

860 Squadron was made up entirely of Dutch aircrew

who had fled Holland after the Nazi invasion.

One of them was Hugo Jellema, a young flight navigator.

She always said that she first saw Dad at the top of the stairs

and she thought, "Hmm, he looks OK," or some such thing!

Aw! All starry-eyed.

Both Hugo and Mary kept scrapbooks of their time in the war.

These record their blossoming romance,

as well as daily life at Maydown.

Their daughters only recently discovered them in an attic.

So she's gathered all sorts of things.

I mean, there's a picture of a band.

"Boy, did they play Take The Train well!"

There's a dinner dance.

"A never to be forgotten night at the club with Hugo.

"Back to Belmont in the pouring rain in evening dress!"

I think there was quite a lot of socialising going on.

-Well-deserved.

-To take their mind off the serious stuff.

Mum was working in the Wrens

-and Dad was back and forth, flying all the time.

-Yes.

It looks from this that they were together a lot,

but I think actually they weren't together that often

because Dad was out supporting the convoys,

flying his various Swordfish back and forth across the Atlantic.

And each of those trips took three weeks.

Look at this one.

"Just arrived. Received your letter. No leave permitted.

"Any chance of seeing you?" Aw, how sweet.

Dad was really very fortunate.

I mean, he did all these things and he had hairy experiences,

but, I mean, he'd tell of other people

-who were not as lucky as he was.

-He came home. Some of them didn't.

A rediscovered wartime film

of their dad's plane about to land on a MAC-ship

gives the sisters an insight into his bravery.

Oh! Oh, my goodness. Looks like they missed that time.

So Dad's telling the pilots how to come down. You know,

"Left a bit, right a bit."

Yeah. Because the pilot couldn't see.

This is him trying to land. Oh, my goodness.

-"Down a bit, up a bit." What a dangerous job that is.

-I know.

Because he nearly gets his head cut off with the wing.

Oh! Safely down.

Oh! There they are!

-I mean, Dad must have only been about 19 then.

-Yes.

-Ditching a crashed plane.

-Oh.

How relieved they must be to actually get out of the plane.

Get out of the crashed one.

Mum must have been quite nervous and anxious about him

all that time he was away. It was a very hazardous thing to do.

-Dad and his mates larking around.

-That's it!

They were pretending that they had to be mad to do this job,

so they were kind of all twitching.

-Oh, that's the Batman.

-Oh, yes!

-What are they doing?

-THE SISTERS LAUGH

It must have been a sunny day. They're out on the deck.

That's what I was thinking, mid-Atlantic,

I was surprised that they would be out sunbathing.

-There's Dad!

-Oh, my goodness!

-He's chewing gum.

-Oh, wow.

70 years later, this forgotten archive shows

a young man still in his teens

trying to lead an ordinary life in extraordinary circumstances.

It's absolutely gorgeous to see. And I feel like

I want to take him out of the screen and give him a hug.

Hugo Jellema crossed the Atlantic

many times and had many narrow escapes.

But he survived the war, not to return to his native Holland,

but to marry his Northern Irish love, Mary Piper.

They lived the rest of their lives together in Belfast.

-It's very emotional to watch that, really.

-Terrific.

-We're very lucky to have it.

-Very special.

The dive team is back on the Rosguill Peninsula, continuing

their mission to map the lost wrecks of the Battle of the Atlantic.

Today they're hunting another U-boat

and this time Ian already has a hunch which one it might be.

As they head out, he shares his thoughts with the team.

-What number have you assigned to this one?

-1104.

-1104.

-What type of sub is the 1104?

-Type VIIC.

-7C?

The dive will confirm whether Ian's right.

But with a heavy swell developing, the divers waste no time

kitting up and dropping over the side.

190 feet from the surface, they have enough light to peer

straight down the conning tower, into the control room.

This is where a German U-boat commander would once have stood

and planned his attack.

The conning tower shows no damage. And the periscopes are still intact.

The U-boat appears to be in good condition.

But just a few yards further on, the hull comes to a sudden stop.

It's as if the U-boat has been snapped perfectly in two.

Why, however, remains a mystery.

The team search for clues to explain what happened, and find no answers.

But, as Ian heads for the surface, one thing is clear.

He thought this was U-1104, a type VII U-boat.

He was completely wrong.

Hang on a second, this is too big. This is just way too big!

It's not a Type VIIC Atlantic. It's definitely a Type IX. Start again.

It's a double mystery for the team. Which U-boat is it?

And how was it broken so cleanly in half?

I can't imagine she ruptured or somebody fired a shell at it,

or whatever. It's a very clean break.

Whoever did the blasting job on that had a work of art.

It sort of adds to the whole sort of confusion of what it is.

So... Back to the drawing board.

So, will naval experts Dr Randy Papadopoulos

and Dr Axel Niestle be able to shed light on the mystery U-boat?

I looked at it and went, "This is not what I was expecting."

Well, from everything we see right now,

it's definitely not the Type VIIC.

Because the deck is simply too wide.

-So this is the aft end of the pressure hull, is it?

-Yes.

There should be two openings in it.

For the two aft torpedo tubes.

-One.

-One, two.

This, at least, solves the mystery for the type.

-This U-boat is a Type IX.

-Yeah.

So this wreck is broken completely and half.

We'll just see the damage here.

Ian shows the two experts

the extraordinary break in the U-boat's hull.

It's unlike anything they've seen before.

-Just look at how clean this is.

-That's amazing.

Absolutely extraordinary.

It's all along one of these pressure hull frames.

It's like somebody sliced it off with a cleaver.

But with only half a wreck,

it's difficult for Axel and Randy to make a precise ID.

Only the U-boat's type and its location are certain, so they scour

German and British files for records of any Type IX sunk in the area.

And at last they find a likely match.

Now, you've been studying the wreck of the infamously named U-broken,

effectively half a U-boat.

Any clues as to what kind of a boat it was and what happened to it?

At the moment, we just can speculate that it is probably U-541,

which, according to the records, had gone down close to this location.

What could have caused that to happen? Presumably something like a torpedo?

If a torpedo explodes underneath, of course,

it will lift up the whole boat bodily

and will be able certainly to break it in part,

but according to the records this boat was not torpedoed.

So what did cause this unusual damage?

In attempting to solve one mystery, the team have stumbled on another.

But from only half a U-boat, they have made a likely identification.

U-541.

This submarine opens the final chapter in Derry's wartime story.

After Britain defeated the German armies in Europe in 1945,

the U-boat fleet was ordered to surrender.

And over 100 submarines assembled on the River Foyle.

Victory was made official when the German crews handed over their boats

and were taken ashore as prisoners of war.

That happened on 14 May 1945

when a flotilla of about eight U-boats came in.

They made their formal surrender on the jetty at the Lisahally

and formerly brought the Battle of the Atlantic to an end.

For the entire war, Derry had battled the U-boat.

Now they were moored in the city.

Locals did everything they could not just to see one but to get on-board.

My uncle, he managed to get me on one of the U-boats,

you could hardly move on them they were that bloody tight.

They were very cramped, you'd wonder how people could have lived on them,

especially under the water.

But the real prize was to get your hands on a souvenir.

And soon Derry was awash with U-boat memorabilia.

Everybody in Derry had something off the U-boats.

Everybody could show you something that came off the U-boats.

I had a friend down the street

who had an identity book for one of the officers on a submarine.

My uncle got an officer's jacket off one of the submarines.

And his brother-in-law ended up

wearing it ploughing fields, you know.

Everybody going to school, you went in with something. Everybody liked to show it.

Dermot and his uncle

managed to swipe a naval chart from one of the U-boats.

And ever since he was a little boy, he's kept it safe.

It was my great treasured possession for a long time, you know.

Showing everybody it.

You will see that they have pencilled in every lighthouse

around the coast of Ireland.

This is where they seemed to zigzag,

perhaps waiting for some ship coming their way, you know.

To me, this was part of the U-boat really coming alive, you know.

But there was more to this surrender

than a formal handover at the dockside.

As part of Operation Deadlight,

the U-boat fleet was towed out to sea and sunk, one by one.

U-541 was just one of over 100 U-boats

deliberately destroyed off the Northern Irish coast.

The idea presumably to put these boats out of reach for all-time?

The prime driver for this frankly is the Royal Navy

which wants to make sure that nobody gets a free supply of submarines

with which it might attack British commerce in the future.

An enemy unspecified.

Operation Deadlight was a dramatic and very public display of victory.

The decision for it all to unfold in Derry was no accident.

It was a formal tribute to the efforts made in the city

to help win the Battle of the Atlantic.

Admiral Sir Max Horton chose the location for that to be Lisahally,

marking the significance of the Foyle in the battle against the U-boats.

Here, after almost six years of struggle, it all ended.

For a city like Derry which had very much been the forefront

of the Battle of the Atlantic,

-there was some justice in this scene unfolding on its river.

-Absolutely.

The residents of Derry had been on the frontline,

so in fact this was an opportunity for them to see the U-boat

that had made their city important to the Allied war effort during the Second World War.

Now that threat is going to be literally gotten rid of.

I think that symbolism gives the residents of Derry and indeed the broader world

an idea that the Battle of the Atlantic really is over.

I think that must have given a real sense of finality to the people

who were watching, and those who got to see newsreels describing it.

This news from the frontline of the battle

was what the world had been longing for.

There were celebrations across the globe, and Derry was no different.

When the word came that the war was over, everybody stopped work.

And everybody was out through the night.

There were dances and singing and drinking and goodness knows what.

The King and Queen made the trip to Derry to congratulate and thank

both the city and the Atlantic crews

for their role in the Allied victory.

Oh, the celebrations were fantastic!

I mean, they were dancing in the streets. The pianos were out,

everybody was out.

I mean, I have that photograph of the one in our street in Albert Street.

Even my granny was there.

There were so many children

and it was so exciting and the bells were ringing.

Everybody was happy. Everybody really was happy that the war was over.

The Battle of the Atlantic had been won.

But there is one final secret on the seabed

that reveals how victory came in the nick of time.

When Germany surrendered, they were only weeks away from launching

a brand-new fleet of revolutionary super-subs.

Deadly vessels German scientists believed would turn the battle

and the war back in their favour.

The Type XXI Elektroboote.

The team is now on the hunt for Hitler's deadliest submarine.

They're excited at the thought of seeing this legendary U-boat

with their own eyes and exploring the wonders of its technology.

OK, any questions from anyone?

Let's get in the water then.

Shots in. Wherever you're ready.

The sunken wrecks of only two operational Elektrobootes

exists anywhere in the world.

And now our team are right above one of them.

210 feet below the surface,

they get their first glimpse of Hitler's secret weapon.

It was over 250 feet long...

..and weighed more than 2,000 tonnes.

It was faster underwater than escort ships on the surface...

And was capable of running and outmanoeuvring any convoy.

It could detect the sound of an enemy vessel

from more than 30 miles away

and could fire 18 torpedoes in 20 minutes,

three times faster than its predecessors.

It was the perfect naval predator.

And her sheer scale leaves the team awestruck.

You see just how deep and how big the hull of the submarine is.

It's just... It's just a scale thing.

I mean, it makes the Type VIIs look like tiddlers.

It's just something else. It's amazing to see.

100,000 men died in the Battle of the Atlantic.

Historians can only imagine how many more thousands of lives

might have been lost if the Elektroboote fleet

had been allowed to enter the fight in significant numbers.

The Type XXI was a game-changer. I mean, completely.

You can see the full transition from a glorified torpedo boat

you could stick underwater, to a totally hydrodynamically designed

underwater fighting machine.

It's fantastic to see such a beautiful streamlined wreck.

It's beautiful in that it's ahead of its time.

It was really the birth of the modern submarine

and you just can't ask for better than that.

It stays in your memory forever, really.

The divers have revealed an extraordinary wreck,

one of the legends of World War II,

submerged just 20 miles off the north coast of Ireland.

For Axel and Randy, the footage of the wreck is an exciting chance

to study in detail a revolutionary secret weapon,

one that symbolises both the deadly threat of the German U-boat

and the wonders of its technology.

It's something that has fascinated the people over the last 60 years,

and here is the real thing. The actual U-boat.

It's not just a blueprint or a picture,

it's the U-boat mostly in its original fitting-out status.

This is the father of all the modern submarines.

It's a nice piece of history to have out there

and really completes the story of the U-boat in the Second World War.

This actually for the first time is a proper submarine -

something designed from the outset

to spend most of its time underwater.

This type is designed for total underwater warfare.

It reminds us the Allies could never really take their eye off the ball.

They had to prosecute the campaign against the U-boat right till the very end.

Absolutely. And from the perspective of the Allies,

the development of the Type XXI U-boat is something they know about.

They've captured U-boat crew members

who have seen these U-boats under construction,

seen them in work-ups, and they get very concerned about them.

That raises the priority for attacking the shipyards

and destroying the U-boats at their source.

Throughout 1944, the Germans did everything they could

to fast-track the new Elektrobootes into production.

Assembled in sections,

they could build a single Type XXI in just eight weeks.

To the Allies it was clear. They had to destroy these deadly vessels

before they could be deployed in the Atlantic.

For example, in a single daylight attack,

they were able to destroy or damage almost a dozen of these boats

still on the building slips.

Wave after wave of Allied bombers

hammered the Type XXIs in the boatyards.

Within months, nearly the entire fleet was destroyed.

They were Hitler's deadliest U-boats,

but only two ever made it into active service,

and neither fired a single torpedo before surrendering.

Now, just off the Northern Irish coast, the team has revealed

the resting place of the last of these lethal machines.

Sent to the bottom during Operation Deadlight.

History, of course, is full of what ifs, but the question I'm going

to ask you is - if the war had been prolonged for whatever reason

and these boats had really taken a hold and their numbers had grown,

it would have potentially had a disastrous effect on the ongoing campaign?

Had the conflict lasted one or two months longer,

a fairly large number of these boats would have appeared in the Atlantic.

Certainly, the sinking figures would have risen to unheard dimensions.

All the historians say it wouldn't have caused the war to be lost,

but it certainly would have made it a hell of a lot longer.

You go away from that wondering what might have been.

And the Battle of the Atlantic would have been a much longer

and even more bloody conflict.

Ian's mission to map the lost wrecks of the Battle of the Atlantic

has unlocked the story of history's longest, most epic naval campaign.

That dive was just the best way to end what has been a real challenge.

So it makes it all utterly, utterly worthwhile.

It's just fantastic, man, you know.

And the team has succeeded in uncovering forgotten wrecks,

revealing technology and tactics of the mightiest of sea battles.

Where else would you rather be?

It's sobering to think all this went off - on a lovely, calm evening like this -

it's sobering to think of it all happening out here.

There's always a story.

The waters off Northern Ireland's coast have at last revealed

the secrets of the forgotten wrecks on the ocean floor.

Even after more than 60 years on the seabed, they still are able to

give off some secrets, there is still something we can learn.

The wrecks tell the story of 37,000 Allied sailors,

36,000 merchant seaman and 30,000 German submariners.

Men who all lost their lives in the Atlantic in the fog of war.

And at the heart of the story - Derry.

Transformed by its vital role in the Battle of the Atlantic

and in the victory of the Second World War.

A city with its own forgotten history.

Its river filled with warships,

home to America's first European military base,

to an underground command bunker

and home to the fight against the deadly U-boats.

The men and women of Derry met the challenges of war head-on.

Theirs is a city with a wartime heritage

that deserves to be remembered and celebrated.

Trying to keep the memory alive, I think

is important because when traces of all of this are gone,

then something from our history

and something from our collective memory goes as well.

Only fragments of this story remain. They should be treasured.

The priceless wartime heritage of an historic city

at the heart of an epic conflict.

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