01x02 - Keeping Secrets

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The Atlantic Ocean.

The scene of one of World w*r II's
bloodiest battles.

The Battle of the Atlantic.

This is the forgotten front line.

It's a battleground that saw the deaths
of thousands of British sailors.

And here, danger was everywhere.

Not only did they have the harsh
Atlantic weather to contend with,

beneath the waves
could be a German U-boat.

Ready to fire a torpedo.

The Battle of the Atlantic is much
more than just a single battle.

It's a bloody and devastating campaign.

In this w*r, we can't just survive it,
we have to win it.

Britain's forces risked
everything they had.

The w*r was an extraordinarily
bloody conflict.

As an ex-Marine,

I'm fascinated by the actions
of the Atlantic's unsung heroes.

Men and women
who kept the Allies in the fight.

Walker was convinced that
the best form of defence was attack.

And as an engineer,

I want to get to grips with these
incredible k*lling machines.

What made them so deadly...

The more ships it took down,
the greater the fame and accolade.

And how they were
eventually defeated.

This time, Britain brings out
its big g*ns.

A ship that could strike fear
into the soul of U-boat commanders.

Secrets and spies.

A covert operation
uncovers n*zi plans.

The locals call it spy house.

And the Allies are forced to unleash an
experimental weapon.

There was an awareness
that we were up against it.

The Germans had outsmarted us.

This is the campaign

that decides the outcome
of World w*r II.

As the Battle of the Atlantic
enters its third year,

convoys of merchant ships carrying
crucial supplies from North America

are under constant attack
from German U-boats.

The losses are mounting.

Cape Verde, a remote archipelago
in the Atlantic Ocean.

It's a warm September's evening
and the waters are calm.

Three German U-boats agree
to meet on this remote island

to restock their torpedoes.

And with the Atlantic stretching out
for more than 40 million square miles,

this rendezvous in a secluded bay on a
remote island in the middle of nowhere.

They're confident that
they're never going to get caught.

But then, just after midnight,
something extraordinary happens.

A British submarine appears.

The German submarines are amazed

that they should be discovered
in this remote location

by a British submarine, HMS Clyde.

This unexpected visitor is captained
by Commander David Ingram.

HMS Clyde lets rip.

Six torpedoes zip through the water
towards the German U-boats.

It's a tough shot.

These are small, fast-moving targets,

sitting not very deep in the water.

The torpedoes miss
and the U-boats dive.

Now the hunt is on.

And then there's a game of
cat and mouse in this bay

while the Germans try to find
the British submarine and

the British are trying
to pick off the Germans.

After more than two hours of searching
for a German U-boat beneath the waves,

HMS Clyde surfaces.

But instantly there is a German U-boat
sailing directly towards them.

The U-boat crashes into HMS Clyde.

The bow rides up onto Clyde's hull

and the U-boat falls back
into the water and dives again.

Without hesitation, Ingram instantly
starts to search for the German boat.

But like a ghost,
it disappears beneath the waves.

The Germans get the hell out of there.

In their minds, they're absolutely
convinced that this guy's not alone.

This guy's got back up.

While the U-boats beat a hasty retreat,

news of the attack
reaches German top brass.

Admiral Karl Doenitz
is immediately suspicious.

What's a British soul
doing in this part of the Atlantic?

He knew that something
must be going on here.

This wasn't a normal course of events.

This remote bay
in the Cape Verde Islands,

this should never have happened.

Has there been a leak,
wonders Doenitz?

Or have the Allies figured out a way
to track U-boat positions?

During the Battle of the Atlantic,
both the British and German navies

communicate amongst themselves
using complex codes.

And both sides live in constant fear
that their codes will be cracked.

After the skirmish in Cape Verde,

Doenitz suspects n*zi communications
have been compromised.

He just doesn't know how.

The answer?

One of the Allies' best-kept secrets

lies deep inside a concrete fortress
in the heart of London.

This becomes the nerve centre
for the Royal Navy during the w*r

and earns the nickname the Citadel.

This is the home of the
submarine tracking room,

where classified intelligence is used

to build up a picture of U-boat
movements in the Atlantic.

And based in here in 1941 is a man

determined to defeat Admiral Doenitz,

Commander Roger Wynn.

Most people have
never heard of Roger Wynn,

but this 37-year-old barrister
is busy developing a strategy

that will help alter the course
of the Battle of the Atlantic.

Roger Wynn was a very unusual figure
to find in the Admiralty.

He had had polio as a child
and so his back was twisted.

He walked with a limp.

He was a highly qualified lawyer
before the w*r.

Wynn knows the German Navy
has around 32 operational U-boats.

His job is to try and work out
where they are and what they're doing.

It's quite interesting the way
both sides in this w*r personalised it.

You have to try and work out
what the enemy is thinking,

you have to try and get
in the enemy's head.

So Wynn puts up a picture of Doenitz

and you know he's looking at him
and he's trying to work out

what's going on in this mind of yours.

What he wanted to do was not just to
analyse what the U-boats had been doing,

but what they might do in the
future to predict their actions

in what became known as
admiralty guesses.

At first these guesses were
rather hit and miss.

But during the summer of 1941

Wynn's insights become
steadily more accurate

because British intelligence
has struck gold.

The Citadel is being sent
information so top secret

it's called Ultra Intelligence.

And it's being sent from a top
secret base in Buckinghamshire

known as Station X.

But to locals it has another name,

Bletchley Park.

Good intelligence is crucial in w*r,

so I've come to Bletchley to find out
how the Allies are getting theirs.

In 1941

this building is home to some of
Britain's brightest brains

who work day and night
to crack the enemy codes

created by one of the most sophisticated
encryption systems on the planet,

the Enigma machine.

What did the Germans use Enigma for?

Enigma is used for sending typically
quite short military messages.

In the naval terms we're talking
about 95% of all wireless messages

sent by the German Navy are sent
encrypted using an Enigma machine.

If Bletchley can crack
the Enigma encryptions

it'll give the Navy ears on n*zi plans
for the Atlantic U-boats.

But the codes are
mind-bogglingly complex.

On a standard Enigma machine,


million possibilities.

So you can't just work through them
one at a time, you'd never get there.

The code-breaking operation
is led by maths genius Alan Turing.

Here at Bletchley

his team have built six special
electromechanical computers

called BOMBS

to help decipher the encryptions.

But it's still taking far too long
to crack the codes.

All this changes in May 1941.

A Royal Navy crew boards
a damaged U-boat in the mid-Atlantic.

They seize what turns out to be
a top-secret cargo.

A working Enigma machine.

And that's not all.

More crucially they get
the associated code-books.

And these books describe
how the keys are created each day.

Now they have the code-books,

Turing and his team can speed up
their code-breaking.

So amazing isn't it when you think
about what was going on right here,

right at these desks.

By the summer they're able to crack
Enigma encryptions within 36 hours.

And feed this vital intelligence

to the submarine tracking room.

So real-time absolutely vital

so that you can redirect your convoys
away from the submarines.

The Battle of the Atlantic
is now a battle of minds.

And one of Bletchley's brightest

is Cambridge graduate
Caroline Rowett.

She isn't a household name like Turing,

but it's Rowett who'll go on to transform
the way Enigma intelligence is used.

By creating a handwritten database
of U-boat activity.

She basically started making a record of
which captain was on which submarine,

how much fuel it's likely to have left,
when it sailed.

Rowett's system enables Bletchley's
linguists and cryptographers

to tap into some serious
U-boat knowledge.

And understanding that bigger picture

is really really important
strategically.

Because if you know how many
submarines the Germans have

operational at any one time,

how many have been sunk.

You know, how many torpedoes
each one's likely to carry,

you can make strategic decisions
about how to fight them.

Intelligence from Bletchley Park
is fed to the Citadel.

And Roger Wynne's
U-boat predictions are

passed on to the Admiralty
next door,

with startling results.

In July and August 1941,

convoy sinkings fall to their lowest
level for almost a year.

For Wynne's nemesis,
Admiral Karl Doenitz,

the turnaround is baffling.

Doenitz started to smell a rat.

Why have you got a hit rate

that's phenomenally decreasing?

It doesn't stack up.

The Allies are back in the game.

By the end of the year,

more convoys are arriving in Britain,

having avoided
a single U-boat attack.

Commander Wynne is delighted
with this success.

But he knows there's a fine
balance to be found

when listening in
on this top-secret intelligence.

If he overplays his hand,

the Nazis could figure out
what's going on and

change their codes forever.

Meaning this precious insight
to the enemy's plans

could be lost.

The Battle of the Atlantic
is on a knife edge.

The tides are starting to turn
in the favour of the Allies.

A secret n*zi code has been cracked,

and this new intelligence,
known as Ultra,

is being used to hunt down
and destroy Germany's U-boats.

But the Royal Navy soon discovered
that actually destroying U-boats

is not as easy as they'd like to think.

Because after two years of
fighting in the Atlantic,

these battle-hardened warriors

have perfected a form of attack
known as the Wolf Packs.

Wolf Pack tactics were
incredibly successful.

This was a new way of doing things.

A means by which
Doenitz could corral

his relatively limited
number of ships

to attack a convoy in a group.

The U-boat Wolf Pack spreads out in a line
along the predicted route of the convoy.

When one of the wolves
spots a merchant ship,

they send a signal
to the rest of the pack.

The key to the tactic is
communication and convergence.

One st*lks and the
rest of them converge,

and when they've all assembled,

then they attack.

At first it was devastating.

The Allies didn't really know
how to counter these tactics.

Time and again,

Royal Navy warships
look on helplessly,

while sudden, violent explosions

send ship after ship
to the ocean floor.

Escort Commander Donald McIntyre

describes the carnage of
a night attack

in 1941.

I had never before seen this
most appalling of night disasters.

We were shocked into silence
by the horror of it,

and the immediate thought
that none could survive.

How exactly are the Wolf Packs able
to penetrate the convoy so effectively?

It's a mystery that will remain
unsolved for another six months.

The w*r that was fought on the seas
was an extraordinarily bloody conflict

that has tended to be erased
from our memory,

perhaps because it was so bloody.

With just under 100 U-boats,

Admiral Doenitz is heaping
terrible losses on the convoys.

His plan is to grow his fleet to 300,

the number he's calculated he needs

to deliver a mortal blow to Britain.

We're aware that in this w*r we can't
just survive it, we have to win it.

So we have to master our shipping lanes
and we have to keep them safe.

Britain calls on the skill and vision
of its naval engineers.

Facing threats on all sides
of the Atlantic means that Britain

has to have a vessel capable
of taking the fight back to the Nazis.

And that vessel is here.

A ship that could strike fear
into the soul of U-boat commanders,

the British destroyer.

As an engineer myself,

I'm fascinated by these
awesome warships

and what makes the destroyer
the perfect ship

to hunt U-boats.

Destroyers were
a crucial part of the convoys

in the Battle of the Atlantic.

What roles did they play
within the convoys?

I think destroyers are just a crucial
part of everything the Royal Navy does.

And they are that
essential multi-role vessel.

Very, very well equipped ship,

very fast,
capable of doing 32 knots.

It's got a huge amount of speed.

These are the greyhounds of the fleet,
so to speak.


the surface speed of most U-boats.

Destroyers are amongst
the fastest ships in the fleet,

built to hunt and to k*ll.

What type of weaponry
were these destroyers equipped with?

The principal weapons
of a destroyer are the g*ns,

so Cavalier has four


capable of taking on aircraft,

capable of taking on surface ships.

She had a set of torpedo tubes,

anti-submarine weaponry,

a series of depth-charge throwers.

Armed to the teeth,

she's also got eyes on her prey 24-7.

All ships of her vintage
had open bridges.

It allowed the watchkeeping crew
to see all the way round.

Which is a great advantage,
I imagine,

as a convoy ship.

And as the Battle of the Atlantic
unfolded and the losses mounted,

then destroyers actually
were just thrown into

every action that was going.

But the convoys are still
losing merchant ships

despite having the ultimate
predator in their armoury.

Their success comes down to largely
the commander in charge.

And one captain in particular,
in 1941,

stands head and shoulders
above the rest.

His name was
Frederick John Walker,

or Johnny Walker, to his friends.

Johnny Walker is a veteran sailor

with an obsession
in anti-submarine warfare.

Known for rubbing his superiors
up the wrong way,

he's been passed over
for promotion.

But in 1941,

he's given command
of a convoy escort.

He had a very different attitude
to most of the admiralty.

Walker was convinced that
the best form of defence was attack.

Johnny Walker's escort
is shepherding a convoy

from Gibraltar to Liverpool.

Under his command are destroyers,

corvettes and, unusually,
an aircraft carrier.

But Walker's escort has a stalker.

The wolf pack closes in.

From the aircraft carrier,

a plane spots a U-boat
on the surface.

And Johnny Walker decides
to do things his way.

Walker goes for it
in a hell of a way.

Using one of his ships to just drive

U-boats into a k*ll zone,

where the rest of his
escort ships can converge

and just flood the area
with death charges

and destroy whatever
U-boat is in there.

And for the U-boat commanders,
this was a very new approach.

They weren't used to the British ships
attacking with such aggression.

And it really made them quite anxious
about attacking convoys.

On his return,
Walker is hailed as a hero.

And the U-boat count
has just risen by five.

With a growing number
of destroyers and

corvettes patrolling the Atlantic,

more vital supplies
reach our shores.

And that very same month,

Britain receives another
major boost in its battle.

America enters the w*r.

The United States of America

was suddenly and deliberately attacked

by naval and air forces

of the Empire of Japan.

The strike on Pearl Harbor
in the Pacific

has huge consequences
in the Atlantic.

Now the U.S. is in the w*r,

Admiral Karl Doenitz
can send his U-boats

hunting in American waters.

Within four months,
up and down the U.S. coast,

U-boats sink more than


The Germans call this
their second happy time.

All the while,

Admiral Doenitz's fleet is growing.

He now has 91 U-boats in play.

And in Britain,

there's a new crisis on the horizon.

For nine months,
the Citadel here in central London

has been receiving key
ultra-intelligence from Bletchley Park.

But on the second in February,

when the head of the submarine tracking
room commander, Wynn, arrives at work,

he's about to discover that
his ultra-intelligence is drying up.

The Germans have modified Enigma.

There was a sort of tense
atmosphere at the time,

here was an awareness that we were
up against it, that we were failing,

and that the Germans
had outsmarted us.

And just like that, the momentum
in this epic battle shifts.

By the end of February 1942,

over 1,200 supply ships
have been lost to the U-boats.

The convoys have never been
more vulnerable.

Churchill knows he has to act.

By early 1942,

the Battle of the Atlantic has been
raging for over two years.

Thousands of lives have been lost,

k*lled in large part by the
n*zi U-boats hunting in wolf packs.

These German U-boats had incredibly
devastating effects on the Allied powers.

There needs to be
a change in fortunes

if Britain is going to push back
against the n*zi U-boats.

The Allies are in trouble.

Setback to Enigma code-breaking

mean British intelligence
is now racking its brains

for other ways
to penetrate n*zi plans.

Behind the doors of a country
pile in Buckinghamshire

runs an operation so secret

not even Parliament knows
of its existence.

The locals call it Spy House

and this place
during the Second World w*r

was one of the most top-secret sites

along with places like Bletchley Park.

And it was here that they bugged

the conversations

of enemy prisoners of w*r.

Latimer House feels
more clariages than cold is.

But thousands of prisoners of w*r
are kept in this jail extraordinaire

so British intelligence
can spy on them.

Wow, what a room, Anne.

So this is the heart of
the operations in many ways.

Where intelligence was discussed,

where key people were briefed.

One of those key people

is the great spy maker himself,

Ian Fleming.

He recruited the naval
intelligence team here

and one of the interesting
interrogators that he enlisted

was a chap called Colin McFadyen.

McFadyen's methods rely
on stealth and cunning.

Here, the walls have ears.

In a set of secret chambers
called M Room,

McFadyen's listeners are eavesdropping

on conversations in cells
and common rooms.

And his spies have ways of making
n*zi prisoners of w*r talk.

Either a prisoner who'd been
turned to work for us

or intelligence officers would
put on German naval uniform

and pretend to be a prisoner and would
lead the conversation in the cells

to a particular way to try
and get the information.

And of course the real prisoner
has no idea that

there are microphones
planted in the light fittings.

And it is extraordinary

the detailed information
that they were giving up.

Prisoners were talking about enigma

and how the codes had changed

and it's stuff which was
passed to Bletchley Park.

And how closely linked
were these two sites,

Bletchley and Latimer House?

Incredibly close working relationship.

What were they after?

To understand the German
fighting capability

and importantly too,

what new technology is
being developed.

The methods used by Colin McFadyen
and his listeners get results.

They discover key pieces
of information about U-boats,

including how many
have been produced

and what their new capabilities are.

The revelations though confirm
Churchill's worst fears.

The Battle of the Atlantic

is about to get much tougher.

It's hard to fight an enemy
you can't see.

And it's harder still

in the middle of the Atlantic Ocean.

The Mid-Atlantic Gap,

an area of over


is out of reach to the
shorter range Allied planes.

Making convoys easy pickings
for long-range enemy bombers.

And the wolf pats.

The hour was desperate.

Something had to be done

to provide aerial protection
in that Atlantic Gap.

This is the Royal Navy solution.

A ship that fires modified hurricane
fighters from a ramp on the deck

using a catapult.

These are the Hurry Cats.

Now I've flown
World w*r II airplanes myself

and I'm not sure
whether this is sheer genius

or total madness.

To find out who will be brave
enough to fly the Hurry Cats,

I've come to meet Harry Raffel
at RAF Hendon.

Harry, when I hear about Hurry Cats,
I often hear the name Louis Strange.

Who is this guy and what did he do?

Strange is an
extraordinary individual.

He won a Distinguished Service Order
Medal from the First World w*r.

And he goes on to lead the training
for First Hurry Cat pilots.

He makes it a point that he will do
the first launches to show that

not only is it safe and can be done,

but that he has confidence in it.

It's quite a mad idea, really,
isn't it?

I mean taking the aircraft off something
that isn't an aircraft carrier.

I think the take-off is probably the bit
which would be most concerning.

You're going at 3.5 g's instantly.

Instantly.

As they come off the catapults,
only just above stall speed,

they have to keep flying level
for enough time to get some speed

before they pull up on the stick
and start to climb.

But a fleet air-run pilot
described it

as the most exciting thing
he'd ever done

and that man had won
the Grand National.

These incredible catapult planes
are hugely ambitious.

It almost feels like their very creation
shows an element of desperation

creeping into Churchill
and those around him's plans.

This desperation is fueled
by the obvious success of

Germany's wolfpack tactics.

May 1942 becomes the most
devastating month of the w*r so far.

U-boats continue to strike
through that month,

sending a total of


plus vital supplies like food,
fuel and materials

to the ocean floor.

Now, it's also
a hugely significant figure

because Doenitz believes that
if those losses continue

over the next few months,

Britain will have no choice

but to surrender.

So, at naval command,

it's all hands on deck

to unlock the secret strategy
of the wolfpack.

After more than two years of
fighting the Battle of the Atlantic,

the outcome is looking
bleak for the Allies.

They've lost their
key intelligence source,

which had given them the edge
earlier in the year.

Ships and vital supplies are being
sunk at a frightening rate.

As a consequence,
food stocks are running low.

Defeat could be
just a few months away.

The wolfpacks are
stronger than ever.

Admiral Karl Doenitz is closing in
on his magic target of 300 U-boats.

The number he's calculated will deliver
a mortal blow to the Allies.

But the Royal Navy has been
working on a plan of its own.

On a train to Liverpool
is a man with a secret mission.

The Admiralty wants to unlock
the mysteries of Wolfpack's strategy,

and they think Gilbert Roberts,

a naval tactician with
a talent for wargaming,

might be the man for the job.

So they're sending him
to a top-secret

command centre for the
Battle of the Atlantic,

known as Western Approaches.

Author Simon Parkin is taking me

to the inner sanctum of naval command

to follow in the footsteps
of Gilbert Roberts.

When he got here,
he met Percy Noble,

who was the commander-in-chief
at the time.

Percy Noble sort of met him
with a high degree of scepticism.

And he said, well, you know,
you can have a room on the top floor,

but don't bother me
with all this game-playing.

Roberts is given
a team of wrens to work with.

One of them is young
Judy de Vivier.

Well, my mother joined the wrens
when she was 19

and was sent into Derby House
to be a plotter on the main plot.

But then she was moved upstairs into
the Western Approaches tactical unit.

Those women were very bright.

They were selected for that.

They were not selected to salute
and say aye-aye, sir.

They were selected to argue.

And they did that.

The wrens and Roberts get cracking.

Drawing a grid system on the floor,

they begin to play out in real time,

an attack on a convoy
that took place the previous month.

Roberts would be the U-boat commander

thinking, right, how can I most
effectively k*ll these convoys?

He had the after-battle reports.

He knew what had happened.

So he was able to lay it out.

The Royal Navy has always assumed

the U-boats fire torpedoes
from outside the convoy perimeter

rather than in amongst the ships.

But in their attic room,

Roberts and the wrens

are about to make
a startling discovery.

It came late one night.

He and two of his senior wrens
were re-staging the game,

playing it over and over again.

He realized that the battle could not
have played out in the way that it did.

The U-boats must have been firing

from within the lanes
of the perimeter.

The Wolfpaks are sneaking
in amongst the ships to fire.

This was just a completely
transformative realization.

That was the eureka moment.

It was.

Next morning, Roberts sends word

downstairs to the office of
Commander-in-Chief Percy Noble.

Roberts describes Noble

of coming into the room
looking icy and snooty.

But when Roberts reveals
their exciting discovery,

Percy Noble grasps its significance.

Percy Noble shakes
Roberts' hands and said,

you've identified a fundamental
misunderstanding

in the navy's approach
to U-boat warfare,

and sends out a message to Churchill

explaining what has been found.

Wow.

Roberts and the wrens

rewrite naval tactics
for dealing with Wolfpaks.

It's a turning point for Allied strategy.

But no w*r game could predict
the deadly twist to come.

The South Atlantic.


the west coast of Africa.

U-boat 156 is
en route to Cape Town.

As dusk falls,

the crew sights a large

liner-turned-troopship,
the RMS Laconia.

Although it was carrying a huge number
of prisoners of w*r and civilians,

it was a legitimate target.

It was an armed vessel.

It carried well over two and a half
thousand people.

On board the Laconia, it's chaos.



the great liner sinks
beneath the waves.

Although the Laconia has enough
lifeboats for everyone on board,

a significant number have now
been taken out of action.

And as a consequence,

many of the 2,700-pound passengers

now face dying in the water.

The U-boat surfaces.

The Germans are after
the Laconia's captain,

but they're shocked to see
so many bodies in the water.

They contact U-boat HQ
and update on the situation,

where Doenitz makes
an incredible decision.

He sends more U-boats to the area,

but on a rescue mission.

As many people as possible
are either put into lifeboats

or even taken on board
the German submarine.

And the U-boat signals out for help.

It says, we've sunk the Laconia.

There are thousands of
people here that need help.

We won't sh**t at you
if you come and help them.

But when the Allies
receive the message

they don't believe it.

They're like, can we trust
this message?

The Germans lay a red cross flag

over the top of the submarine,

and they trail the lifeboats
behind them on ropes.

They hand out food,
they hand out blankets.

This kind of humanitarian response.

Finally, the crew and survivors
hear a plane.

Eventually, you can imagine
the scenario.

On the horizon,
the aeroplanes are coming.

Hurrah, hurrah,
we're going to be rescued.

You know, it's pitiful.

Because they're American bombers.

They b*mb them.

Some of those bombs even
hit the lifeboats.

It's too dangerous
for the U-boat to stay there.

And so, with great reluctance,

the commander of the U-boat
tells the civilians,

I'm really sorry,
I'm going to have to leave.

For the civilians,
this is a terrifying time.

And many of them die.

Very few of them actually
get back to land safely.

More than 1,600 men,
women and children

lose their lives

in one of the most
controversial incidents

of the Battle of the Atlantic.

Doenitz is furious.

He then issues the Laconia order,

where he says, right,
there's no moral compunction

to have to save the enemy,

the drowning enemy,
whether civilian or armed at sea.

Laconia is one of 92 ships

lost to U-boats in September.

As the devastating count grows.

The next few months will be critical

for Britain and the Allied cause.

But in autumn 1942,

at the Citadel in London,

there's a major setback
for the Allies.

Roger Wynne collapses
from overwork.

He won't recover
until the following year.

Despite the crucial work
of the code breakers,

the tacticians and inventors,

the U-boats are gaining
the upper hand.

Britain and her allies
must find a way to fight back

if they're to stand
any chance of winning

the Battle of the Atlantic.