Original subtitles

NARRATOR: Nazi U-boat maestro, Karl Donitz

is winning the Battle of the Atlantic.

- Happy hunting.

PRIEN: One torpedo straight into the magazine, bull's eye.

- One torpedo, one ship.

- This is our happy time.

- (laughing)

- 20 seconds, that must be a record?

DONITZ: Our main weapon has to be the torpedo-carrying U-boat.

NARRATOR:Britain is on its knees.

LAIDLAW: If we keep losing ships,

the country will be down to just a few weeks of supplies.

People will be starving to death.

- May the enemy never know the secret of our success.

NARRATOR:The British are oblivious to the U-boat's tactics.

MATHEWS: You need to get in the minds of those U-boat aces.

(dramatic music)

KRETSCHMER: No way back to Germany this time.

NARRATOR: There are glimmers of hope.

OWTRAM: The capture of the Enigma machine was a huge coup.

- Well, let's find them and destroy them.

NARRATOR: But they proved to be dead ends.

CHURCHILL: Find out what's happening and sink the U-boats.

NARRATOR: The Royal Navy turns to the wrens

to uncover the U-boat secrets.

- That is what we will do here.

By playing through scenarios, and recreating battles, in a war game.

LAIDLAW: So, who thinks they can sink a U-boat?

(morse code beeping)

NARRATOR:Admiral Donitz's U-boats

are hunting British convoys like wolf packs.

They work together to track down their prey

and coordinate their deadly attacks.

PRIEN: Looks like a good day for us.

Enemy convoy in sight.

COMMS OFFICER: AM 1452, north westerly coast.

- Speed? - Eight knots.

PRIEN: About 30 ships, with a shadow convoy.

- (INDISTINCT) - (in German) Jawohl.

- (thunderclap)

PRIEN: The weather to hunt.

St Elmo's Fire, that's an omen.

It's also an omen...

...that Kretchsmer is about!

- Well, I wouldn't want you to get ahead in the tonnage wager.

- We can share the tonnage we send to the bottom.

- Plenty to go around.

- The orders are to wait till nightfall.

- Happy hunting.

NARRATOR:The U-boat captains are driven by a fierce competition

to sink the highest tonnage.

- They got awarded the Knight's Cross

if they sunk a hundred thousand tons of cargo.

This a game of one-upmanship.

Kretschmer, Prien, they are focusing on the prize.

- This is era of the great U-boat aces.

This where audacity pays,

where poor defence of convoys is something the Germans can exploit.

NARRATOR: The competitive U-boat aces

are wreaking havoc on trans-Atlantic trade.

And the Royal Navy doesn't understand their tactics.

DR SYMONDS: By the early spring of 1941,

Donitz's U-boats had sunk a total of 650 ships.

DR RICHIE: You have an island nation where 95% or so of the energy

that Britain requires is brought in from abroad.

70 plus percent of the food stuffs.

It's a terribly dangerous situation.

LAWRENCE: The British are losing so much shipping,

that Winston Churchill issues

the Battle of the Atlantic Directive.

He orders that all U-boats are to be targeted,

and all U-boat shipping yards have to be bombed.

NARRATOR: But it makes little difference.

Donitz protects his U-boats in concrete submarine pens.

Churchill's bombs fail to penetrate them.

- Germany has conquered France.

Because she's conquered France, she now has a sequence of Atlantic ports

that enable her to get directly into the central Atlantic.

NARRATOR:Donitz can attack convoys

leaving the southern ports of Britain with impunity.

So the western approach convoy routes are transferred northwards

to Liverpool and other ports.

The convoy command headquarters is also moved to Liverpool.

LAWRENCE: This was a place of constant activity, 24/7.

The majority of the people working there were the Wrens.

- Morning.

NARRATOR:The head of the Wrens, Vera Laughton Mathews,

wants the Navy to give her team even greater responsibilities.

LAWRENCE: Sir Percy Noble was in charge

of western approaches in Liverpool.

Now, he as a man with enormous experience in the Navy.

- Thank you for coming to Liverpool.

- He was an old hand, he knew the ropes.

But he never really faced something like this before,

and he was desperately trying to find a way

to stop these terrible, terrible losses that were being inflicted

by the U-boats.

- It's a relief to escape the bombs raining down on London town.

- We have our own blitz.

A bomb landed stone's throw away from here, quite a commotion.

- Nowhere safe.

How did the Atlantic Cruise go?

- A real eye opener.

"Bloody chaotic mess" would be a polite way of putting it.

- Did you learn anything?

- I was on a destroyer attached to the escort,

orders from shore were flooding in,

sending the other escort ships, on wild goose chases.

In the end, our destroyer was the only escort left

protecting the convoy.

Poor captain was going stark raving mad.

- Any enemy engagement?

- Thank god, no.

It would have been curtains for us all.

- You need to get in the minds of those U-boat aces,

so they're called. (sighs)

- Well, that's easier said than done, I'm afraid.

- Let me know if the Wrens can do anything to help.

We are here to serve.

- Thank you, I do appreciate having your Wrens here.

It's certainly brightened the place up.

- They can do more than that.

Much more.

- How nice to see you.

STRONG: Vera Laughton Mathews is going to individuals in the Navy

and going, "The Wrens can do this.

The Wrens can give you what you need.

They can fill these positions.

This is powerful stuff."

NARRATOR:Vera Laughton Mathews is determined to transform the Wrens

into a force who can help fight back against the U-boats.

The U-boats had another advantage over the Royal Navy.

They could communicate in secret.

So the Navy could not predict their movements.

- We're back in business.

Send beacon signal, enemy convoy in sight.

Square - AM 1452. Course - 330 degrees.

Report convoy at 12.49. Speed - eight knots.

DR SYMONDS: The Germans sent their messages

through an Enigma machine.

When the operator would hit a key to input a letter,

that would be transferred through three rotating wheels,

each had 26 positions,

so that by the time it was sent out in the ether,

that key had been changed, get ready for this number,

160 quintillion times.

- Send to U-99, U-70, U-A, U-37.

Report by short signal, "yes," when attacking.

STRONG: Donitz is asking for updates all the time,

but these are gibberish, until we can break the code.

NARRATOR:One man who might be able to predict the U-boat movements

through war gaming is Gilbert Roberts.

But his career in the Navy was cut short, by tuberculous.

STRONG: Due to his illness, Roberts, at this point, is in the Home Guard.

Those who can't serve on the front line,

volunteer for service in defence of the UK.

It's better than nothing.

But must have been a heart-breaking experience

for a man with that level of understanding of naval tactics.

(sneezes)

- Who goes there?

Oh, for crying out loud, game's up, let's gather round.

I'm sorry to say it, but if this had been the real show,

we'd all be goners.

You lot are as inconspicuous as a herd of bull elephants.

- It's my lumbago, sir. - I think I've caught a cold.

- Well, better it happens here than when the Germans arrive.

(coughs)

- Are you alright, sir?

- Yes, thank you.

I used to be a 100% fit.

Now my health is just fitful.

DR RICHIE: When he applies to all sorts of jobs with the Navy,

he's told, "Well, no, I'm sorry.

We can't accept you back because of this illness."

STRONG: He wants to be doing something for the fleet.

He's waiting for an opportunity.

NARRATOR:Meanwhile, the Wrens

are using what intelligence the Royal Navy have,

in the Western Approaches Plotting Room.

DR SYMONDS: The Wrens played a key role in tracking the location

of the known convoys, and the suspected wolf pack units.

LAMB: I wanted to be a plotter

because I discovered they had a very interesting job.

The plot consisted of a large map, and you would see all the number

of enormous ships, battleships, battle cruisers, destroyers.

NARRATOR:But the U-boats rarely give away their positions.

Driven by Donitz's tonnage competition,

Prien goes for the biggest kill of his career - the Terje Viken.

A whaling ship, now converted into an oil tanker.

But the main attraction for Prien is not the oil -

vital for the British war effort -

but the fact that the ship weighs over 20,000 tons.

- It's big.

A whaler.

Set torpedoes.

Range - 450 metres.

Depth - nine metres.

Course - 330 degrees, eight knots.

- Torpedoes set.

- Fire!

Direct hit, 30 metres from midship.

- That's a few thousand more tons for our tally.

- Wait.

The beast isn't sinking.

- "Sink the ships." That was the key.

- Go to hell.

DR SYMONDS: Donitz's overall grand strategy

for how the U-boat could win this war,

was to sink as many ships as possible.

Add up the total tonnage.

- Send to U-37, U-47, U-70, U-99.

Report position by squares, by short signal.

Who's attacking the whaler?

DR DUNLOP: He needed to instil competition among them,

in order to increase the tonnage.

He worked out that he needed to sink 700,000 tons of cargo,

every month to win the war.

NARRATOR:This carefully designed competition kicks in.

Kretschmer tries to claim the ship for himself.

But the intense competition makes him and his fellow aces reckless.

It's a flaw in Donitz's strategy, that will come back to haunt him.

- Our turn.

Let's put the wounded beast out of its misery.

Set torpedoes.

- Torpedoes are set.

- Fire!

Hit on the port side.

The crew are abandoning ship.

- We're picking up propeller noises on the hydrophone.

- How close? - Too close.

- Enemy escorts, two of them.

Dive, dive, dive!

- (submarine creaks) - Shh!

NARRATOR:The Royal Navy misses the chance to destroy Kretschmer's U-99.

But Donitz has lost all contact with Prien's U-47.

DONITZ: What's going on?

Are their wireless transmitters down?

Where's Prien and the U-47?

- We don't know, sir.

- Transmit to wolf pack.

U-47, report position, and condition.

Come on, Prien. Where in god's name are you?

LAWRENCE: Donitz never gives up.

He keeps sending out messages going, "Send me your location,"

but he hears nothing.

- Anything?

- No, sir.

- It was all going so well and now silence.

(sighs)

What's Prien playing at?

I bet he's going to claim the tonnage of that hefty whaler.

NARRATOR:While the U-boat aces are obsessed with tonnage,

Vera Laughton Mathews knows that

if she can get enough intelligent into the Wrens, the Royal Navy will,

eventually, run out of male brain power, and be forced to come to her.

And she has a strategy.

MATHEWS: What do you think of the new uniform?

After all, you'll be wearing it.

LAIDLAW: Well, ma'am. I like the hat, I think it's jolly elegant.

- Well, it damn well should be.

I had Edward Molyneux design it.

I want my Wrens to be the talk of the town.

- I shall wear it like a cat on a catwalk

(both laugh)

DR RICHIE: The Wrens are given this very lovely uniform, actually.

I mean, it's designed by a famous fashion designer.

OWTRAM: We had tricorn hats with a badge at the front.

- The trousers are rather fetching.

My father always said,

"A woman should not be seen dead in a pair of truse."

- It's about time we started wearing the trousers. (she chuckles)

OWTRAM: It was a very smart uniform.

Black stockings and brass buttons.

- It looks lovely. Thank you.

LAMB: It made the Wrens very popular to join.

People joined for the clothes, really.

Everybody wanted to join the Wrens.

NARRATOR:As the Wrens fight to have their abilities recognised,

Kretschmer is relentlessly pursuing the crown of tonnage king.

- Sir, we have something.

It's faint, but it's definitely propellor noises, to the south.

- Very good.

Surface and head for that bearing, two-speed.

NARRATOR:Kretschmer, keen to add to his tonnage,

is alerted to a 41-ship convoy,

transporting vital oil supplies to Britain.

KRETSCHMER: We're spoiled for choice.

Let's start with the oil tanker.

Set torpedoes. Range - 1500 metres.

- Torpedoes set.

- Fire!

That's as good as it gets.

Set torpedoes.

There's more than one oil tanker in this convoy.

Fire!

That makes six.

One torpedo, one ship.

Let's head home.

NARRATOR: Kretschmer has just taken his tally

to an outstanding 47 allied ships,

weighing over 273,000 tons.

But flushed with success,

Kretschmer's U-99 becomes complacent.

(distant explosion)

(battleships firing)

- Get up man, get up!

Sound the alarm!

CREW MEMBER: (German) Achtung! Achtung!

(English) Dive! Dive!

- (alarm blares)

KRETSCHMER: Why the devil have we dived?

Are you sure we couldn't have gotten away on the surface?

CREW MEMBER: Yes, sir. The destroyer's 800 metres from port,

they couldn't have missed us.

- Full speed submerged. Let's get out of here.

Those depth charges are too close for comfort.

- (explosion)

- Sir, we've lost all thrust in the propellors.

DR RICHIE: He goes far beyond the depth that he should,

and so is instruments are broken,

so he's forced to rise to the surface.

The British are waiting for him.

KRETSCHMER: Let's get out of here. CREW MEMBER: I'm afraid not, sir.

Electric motors and steering are kaput.

- Radio (indistinct). Now!

(sighs) Give me that.

Two destroyers, depth charges, 53,000 tons, capture, Kretschmer.

Prepare scuttling charges and just destroy all documents and ciphers.

No way back to Germany this time.

NARRATOR: In just over a week, in March 1941,

things are looking much brighter for the British.

Donitz has lost contact with not one, but three of his U-boat aces.

- I need you to find me U-99 and U-100, now!

(slams handset)

Kretschmer... Schepke, where the bloody hell are you?

Don't go quiet on me, like Prien.

Any news?

- The U-37 has passed a message on from Kretschmer.

- "Bombed, boat sunk, Heil Hitler, Kretschmer.

Two destroyers, 53,000 tons.

- Add the 53,000 tons to Kretschmer's tally.

Argh! (objects clatter)

NARRATOR:Donitz knows that Prien is never coming home,

and now Kretschmer and Schepke are missing, too.

- They were like sons to him, his U-boat commanders.

- For Donitz, it was a great shock,

because Prien was the paragon of U-boat ace.

He was a people's hero, and now he was lost.

- When Otto Kretschmer was still alive,

I asked him what he thought was Prien's fate,

and Kretschmer thought it most likely that Prien was hit by one

of his own torpedoes, that he was hit by a circle runner.

NARRATOR: Prien may have run out of luck,

but the truth will likely be never be known.

DR RICHIE: Very shortly after Prien's mysterious death,

Schepke, who was another of the great aces, is also killed.

- I'd like to propose a wager.

LAWRENCE: It's almost as though fate was listening to Schepke

when he was betting his friends.

First to 250,000 tons of shipping buys the champagne.

And within a few days, all of them are taken out.

DR MILNER: Killing two and capturing a third

is a major coup for the British.

NARRATOR:This could be the turning point the British need,

in the Battle of the Atlantic.

DR RICHIE: They think, "We're going to be able to interrogate this guy."

They're going to be able to get something out of him.

- I must apologise for the welcome.

- May I have those back, please?

They were a gift from my leader.

- All in good time. All in good time.

You've made a bit of a name for yourself.

I simply work in the service of the German Navy.

LAWRENCE: Going through the pockets of all of Kretschmer's crew,

the British find this little plan

of how a U-boat would attack a British convoy.

DR RICHIE: The British don't realise the significance

of this sketch, of this diagram.

That this might have been the key to avoiding so many more losses

from the convoys.

- Nobody of importance saw it,

and so the British were still as clueless as ever.

NARRATOR: It's a massive missed opportunity,

but the British do glean one positive piece of intelligence

from the German prisoners.

NOBLE: Very good.

Thank you. (handset thuds)

U-47, that's Prien's boat, correct?

- Gunther Prien's boat.

- Well, we know what happened to Kretschmer, and Schepke,

but it looks as though they lost Prien as well.

Let's say our destroyers got Prien.

Revenge for Scapa Flow at last.

- Very good, sir.

NOBLE: U-boat down.

DR RICHIE: The British use it as a propaganda coup.

They announce the fact that he's died,

and they even drop leaflets over Germany saying, "Wo Ist Prien?"

(door opens)

MATHEWS: A fine morning to you, Miss Laidlaw.

- Ma'am.

MATHEWS: I see the Germans have finally admitted

that rogue Prien is no more.

- I was heartened to see that Kretschmer received

a brisk reception from the good folk of Liverpool.

- Quite.

Let's hope our homegrown inquisition

can eke out the U-boats' dirty secrets from him.

- Thank god, we have got rid of some of the worst of them.

- (chuckles)

I fear there may be many more where they came from.

DR WITT: These three U-boat aces were not unreplaceable.

A new generation of experienced U-boat commanders had grown.

And had learned from the experience of the U-boat aces.

(door opens)

NARRATOR:Karl Donitz,

undeterred by the loss of his three aces is more

determined than ever to win the Battle of the Atlantic.

- Mein Fuhrer.

I'm pleased to report that our U-boats have sunk 90 enemy vessels

and half a million tons of enemy shipping.

But we must do more.

We are on the cusp of great things.

With more U-boats, we can ram home our superiority.

So I must ask again, for the fleet of 300 U-boats.

I will then guarantee you a victory, that will bring Britain to her knees

and will go down in future histories of the Third Reich.

HITLER: I will consider it.

- Thank you.

DR SYMONDS: Donitz would like Hitler to make U-boats the highest priority

but he's fighting against Hitler's commitment to the land war.

And Hitler's just not ready to make that move yet.

NARRATOR: After failing to win Hitler over,

Donitz faces a major set-back

when the British cease an intact U-boat off Iceland,

in the North Atlantic.

But that's not all they capture.

DR SYMONDS: The crew of the HMS Bulldog, this nearby destroyer,

quickly got to the U- boat and were able to conduct a quick inspection.

- They find this extraordinary looking typewriter.

OWTRAM: The capture of the enigma machine and code books

was a huge coup.

DR RICHIE: If we can crack these codes,

then we can know, at least, where the wolf packs are going to attack.

This was an enormous moment of optimism,

of great hope that finally we can get inside Donitz's mind.

DR SYMONDS: At Bletchley Park, a group of eccentric mathematicians,

puzzle solvers, worked hard to try to crack into this code,

and famously built what amounts to the world's first analogue computer.

NARRATOR:Cracking the Enigma code soon brings a breakthrough.

And the Wrens play a key role.

MATHEWS: You've seen the news?

LAIDLAW: Yes, the Bismarck, marvellous.

- Indeed, I'm proud our Wrens in Y Service in Scarborough,

helped hunt the Bismarck down.

On the QT of course.

- Mum's the word.

OWTRAM: You wouldn't talk to your family or friends

about what you did.

I was in the Y Station.

Letter "Y" stood for Naval Intelligence.

We needed to know,

whether German U-boats were lurking to attack our convoys.

So what we were listening to was the radio signals

between German Naval bases and ships.

You would sit down

and you'd start twiddling up and down the wave lengths,

that the German fleet used, and if you picked up a signal,

you would just write down exactly what you heard.

The officer would inform Bletchley Park if it was code.

NARRATOR:Wrens like Pat helped track down the Bismarck,

Germany's most prized battleship.

CROWD: (cheering)

STRONG: In the Bismarck chase, they're gathering intelligence,

they're analysing the positions.

They're predicting potential German courses of action.

LAMB: And they've discovered that they Bismarck was, in fact,

pointing in an entirely different direction.

And they were able to pursue her and sank her.

STRONG: It becomes apparent that the Wrens are really good

at this sort of stuff.

NARRATOR:Thanks to the cracking of the Enigma code,

the Wrens can monitor the German U-boat wolf packs much more closely.

- If you look at what happens to convoys over the summer of 1941,

Germans can't find them, because they're reading the signal traffic,

as the U-boats are sending it, or as Donitz is replying.

The principle means of defending merchant shipping,

is avoidance of the enemy.

NARRATOR: But it's a temporary reprieve.

The Germans regularly change their codes

and it proves impossible to track every wolf pack

so the convoys can avoid them.

This has tragic consequences for the Wrens.

(ominous music)

MATHEWS: The Aguila.

- Yes, I am aware.

- The SS Aguila, the commercial steamer,

was torpedoed and sunk off Spain.

21 of my Wrens were on board.

They all perished.

Had they been aboard a Royal Naval destroyer,

they probably would've escaped the attack!

- A Destroyer was also sunk.

- Don't evade the point.

The point is that my Wrens are not allowed aboard Royal Naval vessels,

because it's considered to be bad luck.

This is pure superstition. It's medieval.

What is bad luck? Is that they were aboard a defenceless freighter?

From now on, my Wrens will only travel aboard Royal Naval vessels,

on foreign assignments! Is that clear?!

- I'm all too aware.

I sympathise with you and, of course,

with the families of all those poor young women.

- Your sympathy is all very well, but I demand action!

DR RICHIE: The SS Aguila tragedy meant

that the Navy had to rethink its policy about women and Wrens

not being able to go on ships.

The law was changed

and finally women were also able to go on board Naval ships.

LAIDLAW: I just heard about the Aguila.

Did you... know any of the Wrens?

- Each and every one.

I personally selected those who went to Gibraltar.

Bright, lovely women.

12 of them were from Y Station, Scarborough.

When I was told, I was in the countryside,

enjoying the sweet aroma of honeysuckle.

And now, I shall forever associate that smell with my girls.

(voice breaks) My poor girls.

- How sad.

And to think, they were all lost on a slow old freighter.

It's a tragedy that will just be repeated.

- No!

It won't... I've made sure of that.

(tram bell dings)

NARRATOR:In September 1941, the British hit a new low

when wolf packs sink 23 ships from two convoys alone.

Despite their apparent breakthroughs,

the Royal Navy seems to be back at square one.

NOBLE: We have the results of the enquiry into convoy SL87

that I ordered.

It does not make for an edifying read.

The fact that seven out of 11 ships were sunk,

with no retaliation against the enemy is to be deplored.

Shocking, I think you'd agree?

- Yes, indeed.

NOBLE: And it's not for want of protection.

"The escort was a strong one for a convoy of this size.

It is clear that the efforts of the escorts were poorly coordinated."

- Understood, sir.

Loud and clear.

- What has become of our invincible Royal Navy?

Never before in my long career have I see such lack of gumption.

- If the Prime Minster gives us more ships, we'd at least have a chance.

- I'm trying, I'm trying.

But we must deal with these U-boats once and for all.

- Leave it to me, sir.

DR RICHIE: So Percy Noble realises that if they do not find a way

to stop this terrible U-boat menace from sinking all of these ships,

that the British are going to have to capitulate to Hitler.

- The problem is we don't understand how the Germans are operating.

- Our agents in Spain have sighted a convoy in Gibraltar.

- How many ships?

- 32 merchant vessels, protected by escort ships.

- Send a message to U-67.

Tell him to monitor the convoy.

Put the other seven U-boats on standby to attack.

DR SYMONDS: HG76 is the 32-ship convoy,

but with 16 escorts, plus an auxiliary aircraft carrier -

The Audacity.

And the escort group is commanded by Frederick John "Johnny" Walker.

COMMS OFFICER: HMS Stanley reports

that she's under attack by a submarine.

- Those damn German hearses. Where are they?

Fire a flare!

(flare whooshes)

Blast!

Buttercup stern.

COMMS OFFICER: Contact, 1200 yards.

DR MILNER: They've got modern radar,

and the great advantage of radar is it provides the kind of intelligence

that Walker needs to tumble the battle in his direction.

- Fire depth charges.

Prepare to ram.

(metallic creaking)

- What's going on?

- It's radio silence from our U-boats.

- Order another three U-boats to join the wolf pack.

Tell them to re-group for another attack.

We need to sink this convoy.

CREW MEMBER: We're being pursued by more U-boats!

- Well, let's find them and destroy them.

Buttercup starboard.

DR RICHIE: Walker comes up with this idea of Buttercup,

which is to turn his ships outward

and to try and go over where the U-boats are.

- Come into our little trap.

STRONG: His assumption is that, if he illuminates the entire area

and moves out into the periphery,

he will be able to pick one or two of these U-boats off.

- The problem is, it lights up the aircraft carrier Audacity.

WALKER: For god's sake.

It must be the Audacity.

DR RICHIE: This is a ship that, of course,

the U-boats can then identify and they sink it.

- Let's even things up.

Fire depth charges.

Come on.

Buttercup has prevailed.

DR SYMONDS: Four ships are sunk, but so are five U-boats.

You call that a victory for the convoy in that case.

- We've lost 5 U-boats.

- Five U-boats?

We can't let this happen again.

Have they changed tactics?

OFFICER: We've seen no evidence of that.

They managed to blunder into our pack.

- They must be using some new technology

to help find our wolf packs.

NARRATOR:The British believe they have found a repose

to the U-boat menace, thanks to Johnnie Walker.

- Congratulations, Walker.

You've delivered a long overdue message to the Nazis

and their damned U-boats in the best Naval tradition.

- Thank you, sir.

Although, you should thank Buttercup.

- Buttercup?

- It's my pet name for my wife, Eileen,

and it's the codename for the tactic we came up with

to give Jerry a taste of their own medicine.

- I'm sorry?

- The idea of Operation Buttercup

is to force the U-boats, the hearses, to dive.

The easiest way to finish off a submarine

is underwater with depth charges.

We illuminate the sky so that we can see them

if they surface and try to slip away under cover of darkness.

- I see.

I'd like you to write up this Buttercup manoeuvre in full,

so that I can issue it

as part of our escort group operational instructions.

Well done, Walker.

(glasses clink)

Thank you, sir.

STRONG: Walker, a superb commander,

arguably the best ace of the war,

but at the same time,

he hadn't discovered the way the Germans were operating.

That took other minds, in another place.

(knock on door)

- Hang on!

(coughs) Hang on!

- Commander Roberts?

- Yes, I was told to expect you.

NARRATOR:Serious doubts have been raised on high about Buttercup.

Senior British Admirals suspected it is another false dawn.

ANDREWS: The Royal Navy has to find a fresh approach

to Donitz's tactics in the Battle of the Atlantic.

They find Gilbert Roberts in an unusual place,

training the home guard, retired, a survivor of tuberculosis.

- May I ask where you're taking me?

DRIVER:London, sir. The Admiralty.

- Can I ask why?

DRIVER:No. Orders.

- Mystery tour.

What fun.

LAWRENCE: Roberts is whisked up to London

for a meeting with Cecil Usborne.

Now Cecil Usborne is an aide to the Prime Minster, Winston Churchill.

USBORNE: Commander Roberts,

thank you for coming at short notice.

ROBERTS: It was an invitation I couldn't refuse, sir.

- Yes, good.

Straight to the point.

It's clear that something needs to be done

in the Battle of the Atlantic, or we will lose the war.

Simple as that.

The Prime Minster is most worried.

Merchant ships are being sunk at far faster rate

than we are able to replace them.

That's where you come in.

I hear you've developed some interesting ideas about war gaming?

- I have, sir.

It's become something of a preoccupation. (coughs)

- Good.

We need to do something about the U-boats.

A fortnight ago we had a breakthrough.

Captain Johnnie Walker was escorting a fleet out of Gibraltar.

Faced with a full on U-boat attack, he managed to sink two.

In all, we sank five.

Walker, somewhat flush with his success,

called the whole thing Buttercup.

- Buttercup?

- It's what he calls his wife, I believe.

That's all well and good, but with my tactical hat on,

I rather wonder whether Walker's success was not down to Lady Luck.

- Lucky Buttercup.

- One more small thing, before you go to Liverpool.

- Liverpool? (phone rings)

- Ah, yes, sir. We are ready.

CHURCHILL: Find out what's happening, and sink the U-boats.

- Um, well, yes, of course.

- Time is not on your side, Roberts.

You must uncover the U-boats' dirty tricks,

by recruiting and training a war gaming team.

Got it?

- Yes, sir.

NOBLE: A school to play games?

- And I'll need men to staff the unit, too.

- All my best men are at sea.

MATHEWS: I hear you're in need of staff.

- Sir. - The Wrens?

ROBERTS: Ladies, if we lose the Battle of the Atlantic,

we lose the war.

- Sir, the board is set.

WALKER: Buttercup works.

LAIDLAW: The Royal Navy are relying on luck to protect the convoys.

- We need to analyse U-boat attacks, and find a tactic to destroy them.

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