Code-Breakers: Bletchley Park's Lost Heroes Timewatch

This is a British mathematician called Bill Tutte.

You won't have heard of him.

But in 1943, he pulled off what many believe

was the greatest intellectual feat of World War Two.

It shortened the war and saved millions of lives.

He died in 2002 without ever being officially recognised

for his achievement.

This is a former GPO engineer called Tommy Flowers.

In 1944, he turned Tutte's mathematical ideas

into the world's first computer.

He died in 1998.

Chances are, you won't have heard of him either.

Backed by the brightest talents of Bletchley Park,

they allowed Britain to break a top secret machine

employed by Hitler to dictate the course of the war.

This machine was NOT Enigma.

It was something far more secret and significant...

and you definitely won't have heard of that.

It was Hitler's Blackberry really.

That intelligence probably shortened the war by a couple of years.

They were the forgotten heroes of Bletchley Park.

This is the story of a secret war and how two men changed the world

and then disappeared from history.

This is Bletchley Park.

In 1939, it became the wartime headquarters of MI6.

If you know anything about what happened here,

it will be that a man called Alan Turing

broke the German naval code known as Enigma and saved the nation.

And he did... but that's only half the story.

There were three heroes of Bletchley Park.

The first is Alan Turing.

The second was Bill Tutte who broke the Tunny system,

a quite amazing feat.

And the third was Tommy Flowers,

who, with no guidelines, built the first computer ever.

Amazingly, the story of Tutte and Flowers has never been fully told -

but then again, Bletchley is Britain's fortress of secrets.

The secrecy about Tunny and Colossus

has completely distorted the history of computing

and it's also left the story

of the World War Two codebreaking effort incomplete.

It's like there's not enough room on the stage

because the Enigma story has taken up so much space.

It's not surprising that there are stories

still to be told about this place.

Bletchley Park was Churchill's house of secrets.

It didn't even appear on any map.

Nicknamed "Station X", this sprawling complex was home

to a clandestine army engaged in a shadowy struggle

for military intelligence.

Bletchley Park's codebreaking history began in 1939,

with a tiny attic radio station hidden at the top of the house.

It would eventually give its name to the entire estate.

Station X.

As the war progressed, operations expanded out from the main house

to a haphazard collection of huts and concrete blocks.

Here, some of the most brilliant minds in the country

were involved in a constant battle to learn the enemy's secrets.

Arguably, the toughest and most rewarding struggle

was against a code called "Tunny".

In defeating it, Bill Tutte and Tommy Flowers

would change the world.

Captain Jerry Roberts worked alongside Bill

and was involved in the attack on Tunny.

He is the last surviving codebreaker from an elite group

known as "The Testery".

Now aged 90, this is the first time he has visited this part of the Park

since the war.

General Eisenhower said Tunny decrypts

shortened the war by at least two years.

In its heyday, the place was really buzzing.

Thousands of people working here, hard.

Very disappointing to see it in this shape.

The Testery were backed by a huge team of people

processing the information gained from the broken codes.

And while much of Bletchley has been restored,

the places that housed those workers are abandoned.

The secrets they uncovered, though, are still coming to light.

World War Two was a conflict uniquely designed

to create secret messages and exploit them.

The rapidity and mobility of armies during the Second World War

meant that you couldn't get your fixed-line communications,

which are much more secure, up quickly enough.

So increasingly, they came to rely upon radio technology

and radio technology, of course, is broadcast to the world

and they would, therefore, be able to intercept it.

It's a considerable weakness.

If you could break into the right encoding system

then you could deliver victory.

That was what Bletchley was built to do and their most secret

and stunning success came against a code which they nicknamed "Tunny"

and the Germans called "Lorenz".

Its existence was a tightly guarded secret.

Even now it's not common knowledge.

Tunny was generated by a new top-secret machine,

a device Hitler called his "Geheimschreiber" -

"The secrets writer".

To understand its genesis and the need for this super code,

you first have to look at the system that preceded it.

Enigma.

Enigma would dominate the early work of the codebreakers

of Bletchley Park, and it was a formidable opponent.

Well, this is an Enigma machine, a type of cipher machine

that was used throughout the Second World War by the Germans.

Throughout the Second World War, they believed that the ciphers

that were made on this machine could not be broken.

If I press the key for letter "N", lamp "W" lights up on this occasion.

So "N" would be enciphered into "W".

If I release my finger and press "N" a second time, on this occasion,

lamp "M" lights up, and the reason for that

is the rotors at the back of the machine have moved

each time I press a key and that changes the internal wiring.

Enigma masked Germany's wireless traffic.

The Morse code transmissions that were monitored back in Britain by "Y Stations",

monitoring and recording stations,

operated almost exclusively by women.

From the First World War, there was considerable emphasis put on

the quality of wireless receivers.

You might think that the most important thing in wireless

is the transmitter or the medium, the ether through which messages travel,

but for the cryptographers,

the main thing was the quality of the receiver,

being able to pick up the last lingering trace of a message,

and that was where the British radio engineers

were considerably more advanced than their German counterparts,

and the Germans simply didn't believe that their messages

could be picked up as far away as they were.

They didn't believe that messages from Russia, for example,

could be picked up in Britain.

For the first years of the war those listening posts

were dedicated to picking up Enigma traffic.

Then, in 1941, a new and strange sound

began to be picked out from the ether.

"A new kind of music", it was described as

by the British listeners when they first heard it.

This strange music was a new coding machine delivering messages

not by Morse, but by teleprinter.

The information war was about to move into new territory.

The advent of machine-made codes had one immediate effect

on Bletchley Park -

they began to recruit mathematicians.

Mathematicians were regarded as weird, incomprehensible people

and it just wasn't really understood what contribution

they could make to code-breaking.

These machine ciphers that were introduced, Enigma and so on,

and there were others as well,

are incredibly complex mathematically.

I mean, the First World War,

the British code-breakers were wordsmiths,

people who translated ancient documents for example,

cos it was all about words,

but in the Second World War it was much more about mathematics.

The mathematicians were thrown into the front line

against this new mystery system.

Even though the Nazis believed Enigma was unbreakable,

Hitler demanded more security.

His style of command called for a new and more direct

communications network. It would carry more information

and supersede the tangle of Morse traffic which his forces generated.

Enigma was really out of date technology

by the time the war started.

Three operators were required

and then another three operators at the receiving end.

There'd be the guy who actually typed the message,

the operator would have an assistant who would painstakingly note down

the letters as they lit up,

and then that would be handed over to a radio operator

who would translate that into the "dit-dit-da" of Morse code.

BEEPING

And then the process was reversed at the other end.

So you had six people co-operating in the transmission

of a single message with Enigma. Very slow, very clumsy.

So the vast volumes of information needed to fight a modern war

at that time would simply have overwhelmed a system

based upon using an Enigma machine, so they needed something which would

cope with the throughput of information required.

And this is it. The machine Hitler had dreamed of.

The Lorenz SZ40.

Or as the Allies called it, "Tunny".

This is an example, quite a rare example,

of what is called a Lorenz enciphering attachment.

Quite a complicated machine.

If I lift up the cover and show you the interior.

If you count up, you'll find that this device has got 12 wheels in it.

The Lorenz was much more sophisticated than Enigma.

The operator at one end typed in plaintext

and the operator at the other end received the plaintext

on his teleprinter without any intervention on his part.

The way in which this Lorenz cipher machine worked was it would apply

two layers, two keys, to your message,

so it wouldn't encipher it once, it would encipher it twice.

The first encipher used five wheels.

Then they would apply a second key

and this used similar five wheels and they had another two wheels

that were called, what we called "stutters" in the key.

And then that would generate a repeat character

and this was in order to try

and introduce this apparent randomness into the key.

The 12 wheels made the machine an awesome generator of code

and the number of potential ciphering possibilities

multiplied out as...

which equalled 1.6 million billion combinations.

Another innovation saw the Lorenz

incorporate the natural code of the teleprinter into its basic design.

It's kind of modern binary code really.

It's zeroes and ones and they just took the teleprinter code

and they encrypted that.

With the Lorenz enciphering device, the plain text letter "A"

was changed by a machine which actually added to it

a pseudo-random character, for example, the letter "K"

might have been used, for which the teleprinter code was this -

four crosses and a dot and these two characters were then combined

together by a process which is sometimes called "addition".

If the two elements were the same then the result was always a dot.

But if they were different, the answer was a cross.

And here, they're the same so it's a dot.

And if you looked at that set of impulses in terms of

the standard international teleprinter code,

you would find that that was, in fact, the letter "N".

The letter "A" has been enciphered to "N"

by adding this random character "K" to it.

Now, at the receiving station, of course,

the letter "N" is the cipher message

and we already know that that's going to come in, in terms of this pattern.

And now, a little bit of magic...

If at the receiving station the same random character that was used

by the sender was combined with it, in the same way...

Adding up... Two, these are different so the result's a cross.

They're different, the result's a cross. Same, a dot.

These two are the same, a dot. And these two are the same, a dot.

The result would be that. And if we look back,

that of course is the old character "A"

which was the original plaintext.

The actual number of teleprinters using this code

in the new network was less than 30.

But they were the lifeblood of the German command,

feeding out to the furthest fingertips

of the Third Reich's reach.

More importantly,

as many of the generals needed information about other campaigns

as well as their own, one line of traffic could produce an insight

into the entire German war effort.

This was the prize awaiting the codebreakers.

To get to it, they had to crack a code no-one understood,

produced by a machine no-one had seen,

and with a range of possible encryptions

that were utterly unimaginable.

To defeat the impossible machine, Bletchley would turn to

a 24-year-old mathematician called Bill Tutte.

Bill was born in Newmarket in 1917, the son of a gardener

at Fitzroy House, a local racing stable.

As a child, his keen intelligence soon showed itself.

He gained a scholarship to Cambridge and County High School.

After winning the scholarship, Uncle Bill faced

the even greater feat of getting to and from the school,

which was roughly a 12-mile journey there

and then 12 miles back again.

So he definitely had a lot of determination.

At his new school he excelled,

winning prizes in every subject.

I imagine he might have been frustrated at the school itself

in that he was apparently so much ahead of all the other pupils

so he would've been a bit isolated in that respect, I imagine.

In 1935, he went to Trinity College, Cambridge

where he studied chemistry and then mathematics.

Bletchley's habit of raiding the best academic talent

meant that Bill was sent to the Park in 1941,

although not everyone recognised his potential.

He first was interviewed by Alan Turing

and was not chosen to work on the Enigma project.

However, that was the best thing that could have happened to Bill.

Instead, he was chosen by John Tiltman

to be part of the research group.

They were the cream of the cryptographic people.

Bill found himself in the right place at the right time.

After months of fruitless examination,

the team working on the invincible Tunny code

were about to be gifted a way in.

At the beginning, the Germans were very sloppy.

They obviously had so much confidence in the machine,

they were over-confident.

In fact, this is how we came to break the system.

You need depth to break any cipher.

By depth, I mean a number of messages sent using the same key

or the same system.

30th August, 1941.

A German operator had a long message of 4,000 characters

to be sent from Athens to Vienna.

What happened is they sent the message

and the person at the end said, "Well, I didn't quite get that.

"Can you send it again?"

The German operator went and sent it again,

but he didn't change the wheel settings,

and so we got what we called the depth,

two messages with exactly the same encryption.

So he sends the same message

on the same setting,

and the trouble is then that when he resends it,

he makes slight differences in the punctuation,

so the message isn't quite the same as it was.

He abbreviated Nummer, the German word for "number", to "Nr",

so he didn't have to type in the U-M-M-E every time,

and anything he could abbreviate, he'd abbreviate it.

An intercept station picked up these messages.

They realised that they were radio teleprinter.

The message was sent to Bletchley via a despatch rider.

When it got there,

the first person to attack it was legendary codebreaker John Tiltman.

A former frontline soldier in World War One,

Tiltman was awarded the Military Cross.

But it was his talent for languages

that saw him rise through the ranks in intelligence work.

He's generally recognised

as one of Britain's best codebreakers in the Second World war.

He did achieve quite a lot on Japanese codes, for example.

He taught himself Japanese in just a few weeks.

But he looked at this Lorenz cipher and he was the first to realise

that there was a method of breaking through this code.

The Lorenz machine had a particular weakness.

If two messages were sent with the same key sequence,

then there was a way in which the signals could be recovered.

Let me show you.

We had a message earlier where the plaintext was letter A

and the pseudo-random character generated by the machine was K,

and the result turned out to be the letter N.

Now, suppose another plaintext message B was sent

using the same key.

Then on this occasion the answer to that in fact turns out to be P.

I'm not going to show that,

but it's the same procedure as we used before.

Now, we saw previously

that if you add K to this message you recover the plaintext.

Suppose you add those up,

so that on the left-hand side you've got A + B + K + K.

Now, the elements of those two in each case will be identical,

they'll cancel each other out,

and in effect the K disappears from the equation.

And of course, on the right-hand side we've got N + P.

N + P, from the teleprinter code, is in fact the letter G.

And so we can say that this is what we've got.

We've got G, the sum of the two pieces of cipher text,

and the question is, is it possible to decompose that

back into the original messages, which were of course A and B?

That was what we would like to do.

Well, there's no mathematical way of doing it,

but one way in which it CAN be done

is to make an inspired guess for one of those answers.

Suppose, for example, we made a lucky guess

that the first message was just the letter A.

Then if you take the G we've got and add A to it,

then from the teleprinter code, if you add G and A together

you discover that you do get B, the second one.

And so if this make sense, that makes sense, and you've got a result.

A second, more convincing example, perhaps, is this one,

which is based upon six letters.

..is the sum of, in teleprinter world,

the names of two principal cities in the United Kingdom.

Now, the question is, could we resolve that

into the actual names of these cities?

And the method they used at Bletchley was based upon

intuition and perseverance.

For example, if you've got two important towns here,

it's conceivable that one of them might well be London.

And so a good try...

And then proceed to add these pairs of letters together

using the teleprinter code method I showed you earlier.

We won't do those. It'll take us too long.

But I assure you that if you do, you come up with this result.

Now, it might be argued that that could have occurred by chance,

but it's very unlikely,

and so this approach was one that was used at Bletchley Park

to decompose these combined messages.

Colonel John Tiltman would take such a message

and he would use a plausible piece of German,

something he thought might well occur at the beginning of one of the messages,

add it into the composite

and see if something in plausible Germanic came out as a result.

Tiltman took ten days to hand-break and unravel the transmission.

In his extraordinary feat, he manages to extract from this

the cipher text,

what was the cipher text, what was added to the plaintext.

It was a phenomenal piece of decryption.

But it still didn't help the team understand

how they could regularly read Tunny.

He couldn't work out the system -

how the machine worked,

and the job was passed to Bill Tutte.

Tutte sort of recalls it as almost an act of desperation -

"Oh, well, we can't work it out - here you are, you have a go at it,"

almost disparagingly, you know?

And Tutte sits down and he sees patterns.

He's looking for patterns.

And he did put this 4,000-word message into columns

and made a rectangle out of it,

and he thought about what might be a useful length of this.

And then he noticed that there were certain repetitions

that went across the rectangle.

He realises that there seems to be a pattern every 23 times, a rotation.

He thinks it might be 25, so he tries multiplying 23 by 25

to see if the pattern extends along that.

And it doesn't quite work,

but the pattern does extend along 574.

So he thinks then,

"Ah, well, maybe it's 41,"

because 41 is a prime number of 574.

You wouldn't have a machine that rotated through 574 positions.

"Maybe it's 41." And he tried it, and it worked.

From that, he began to deduce,

"Well, this starts repeating itself after 41 strokes,"

that you get a certain resonance

that even though it's affected by other impulses,

the dominant thing is here the fact that you get this resonance after 41.

So he says, "Well, I think the first wheel in this has 41 spokes."

Then he starts working on the second wheel, and so forth.

I was working in the same office as Bill Tutte for most of that time,

and I can still remember him staring into the middle distance

and making counts on reams and reams of paper.

And I used to wonder whether he was actually doing anything!

My word, he was! The most extraordinary achievement.

Using Tutte's insight and a method known as Turingery,

the Testery applied brute mental force to break the code.

As they did, it became apparent

just what a valuable source of information Tunny would prove to be.

We saw the signatories and we saw who the messages were sent to.

So we were well aware of all that.

And they included

Field Marshal Keitel, who was the head of the whole German army,

which was not a bad start,

and Jodl, who was the Chief of Staff of the German army,

in other words the chief operating officer,

and his number two, Warlimont.

But in 1944 they were joined by a fourth -

Adolf Hitler himself.

You're almost in the High Command meeting,

where they're working it all out. You are almost actually the fly on the wall.

The world's toughest code had been broken.

Hitler's secrets were laid bare,

and the course of the war was about to change,

all because of one sloppy, lazy error

by a lowly teleprinter operator.

I think this German operator did us such a huge favour,

I think there ought to be a statue of him in Whitehall.

The first chance for Bletchley Park to use Tunny information in the field

came at the battle of Kursk on the eastern front.

The Testery, the elite group commanded by Major Ralph Tester,

were still breaking this impenetrable code by hand.

Even so, they had uncovered an incredible amount of information

regarding plans for a massive surge by Germany

against the Russian forces.

The Tunny decrypt showed that they were about to make

a major assault on the Russian lines,

and we were able to warn the Russians.

But much more than that,

we were able to tell them how the attack was planned.

"It's going to be a pincer attack."

And even more astonishingly,

we were able to give them the whole order of battle.

It was the Nazis' last chance to put the Red Army on the back foot,

but the Russians, forewarned and forearmed, were waiting for them.

Kursk was both the largest armoured clash in history

and the single bloodiest day of aerial warfare ever.

By the end of it, Germany's Russian campaign was in tatters

and the Red Army gained an initiative they would press all the way to Berlin.

The Russians, of course, called Kursk "the turning of the tide".

Kursk proved just how important intercepted Tunny messages could be.

The challenge now was to accelerate the decoding process.

I've got a page up here that mentions Bill Tutte.

It says that he invented what they call...

the "1 + 2 break-in method was invented by William Tutte in November 1942."

What Bill did, his first achievement was

he actually diagnosed the machine, the structure of the machine

and how the cipher worked, purely from intercepted messages.

Nobody had actually seen the machine at all.

But then, his second major contribution

was working out a statistical method of cracking the machine.

The hand methods that they had used up until then were no longer possible

because of extra German security measures and so on,

so they were coming to an end of what they could do in cracking these messages.

And then Tutte worked out this method.

It was a mathematical and statistical attack on the coded messages,

and it required a huge amount of checking and counting of data.

Luckily, at Bletchley Park there was a man who had an idea

how this work could be done.

Putting Bill Tutte's theories into practice

led to one of the great technological breakthroughs

of the Second World War,

a breakthrough kept secret for nearly 60 years.

It was made by a GPO engineer called Tommy Flowers.

Flowers was a brilliant man.

He was quiet, he had a slightly hesitant manner.

He looked very boyish,

and with his hair perpetually smarmed back with Brilliantine,

he didn't look like someone who was about to change the world.

But change the world he did.

Tommy Flowers was born in Poplar, London in 1905,

the son of a bricklayer.

He was born into

a Cockney-speaking world,

and Flowers kept his accent, to a greater or lesser degree,

right through his life,

and he said later in life

that his Cockney accent had probably been a handicap to him.

His brilliant mind enabled him

to move out of that world into a quite different world.

Like Tutte, he was a scholarship boy,

but he would gravitate to industry rather than university.

First, he did an apprenticeship in mechanical engineering

before gaining a degree at night school

and rounding off his education at Dollis Hill,

the Post Office's unique research laboratory in London.

Bletchley used the Dollis Hill engineers to help with their attempts

to harness machines to the task of codebreaking.

This is how Tommy came on to the radar of a pivotal figure at the park,

the mathematician Max Newman.

He discovered that you could mechanise

Tutte's method of breaking this cipher.

He understood that it was something that you could put into a machine.

Max's department, called the Newmanry,

had built a machine to crack Tunny.

Nicknamed Heath Robinson, it kept breaking down.

Newman brought in Flowers to fix the Robinson,

but Tommy had a better idea.

Tommy Flowers took one look at this and said, "I can do that better."

I can have the patterns generated in electronic circuits,

and now I've only got one tape, which is the source tape, the cipher text.

I can read that now at 5,000 characters per second,

compared with 1,000 on Heath Robinson.

And I can now generate these patterns in electronic circuits.

But, of course, that meant that he had to have

vast numbers of valve tubes in order to do this.

Valves were flaky kind of devices,

and the more of them that you had, the greater the probability

that a couple of them would be out of action at any time.

But Tommy's practical experience meant that at that time,

he knew more about the potential of this technology

than anyone else in the country.

He knew that if you left electronic valves running for a long time

then you didn't get problems with them.

The problems arose if you kept switching them on and off.

Flowers knew he was right,

so he just went back to his laboratory at Dollis Hill

and quietly got on with building the electronic machine

that he knew the codebreakers needed.

It was massive, the effort that was required to do it.

Flowers told me that he and his group worked until their eyes dropped out.

Eventually, he produces this thing and they try it out,

and it works first time.

"Oh, gosh, that's luck." So they try it out again.

And it works second time, and it keeps working,

every time they try it out. And they're so...you know,

"Good grief!" And he produces this thing called Colossus,

which is the world's first semi-programmable electronic computer.

This is Colossus.

And what it did was, you took the intercepted cipher text,

on a lot of paper tape.

Five bit code there. And that is received by us on our radio station,

planked on a paper tape,

and loaded on to this part of Colossus here, called the bedstick.

That's the part of Colossus that holds the intercepted

cipher signal, and that is joined into a loop,

and being read continuously.

And that is being read at 5,000 characters per second.

That's the data going into Colossus.

They put the results of those readings up on to a lamp panel here,

and here are the results of a particular run.

So this is refreshed every time the tape goes round one continuous cycle.

We got one document that was written at the end of the war.

A Technical Description of Colossus 1.

It's a sort of technical manual that describes

the different types of valves that were used, for example.

And the different parts of the machine,

the circuit diagrams of the valves

that were used in the different parts of the machinery.

Internal bitstream generators, the clock pulse system and what have you.

Which were all, nowadays are standard parts of any computer,

but all had to be invented for this machine from scratch.

Now, as I say, they have been taken over and used in modern day computers.

As innovative as it was, Colossus would only break the two chi wheels.

Decoding Tunny would still be a team effort.

There were seven stages to the breaking of Tunny.

And, uh, whilst the Newmanry was established,

the Newmanry handled two of them,

and then the Testery handled the other five.

PHONE RINGS

Bletchley Park's scepticism was immediately cured

as soon as they sa2 Colossus working.

They wanted more machines.

A little unrealistically, they asked for four more Colossi

by the 1st June, the projected date for D-Day.

As it was, Tommy and his team

only just managed to deliver one more machine, the Mark II.

It was 1am on the 1st June,

and Flowers and his men just had to go home to catch some sleep.

Flowers left one of his right-hand men, Bill Chandler,

to carry on the fight alone, through the small hours of the morning.

It was a very tough night for Chandler. He worked on, and about 3am

he noticed that his feet were in a pool of water.

A radiator pipe on the wall had burst

and water was inching inexorably across the floor

towards high-voltage equipment.

It was quite dangerous, I think, for Chandler, but he carried on

and eventually, in the wee small hours,

he tracked down the fault

and he made some adjustments using his soldering iron,

and Flowers turned up a few hours later to find

Colossus working perfectly.

No one had managed to fix the leaking radiator pipe, though,

and the people operating Colossus had to wear Wellington boots

to insulate themselves.

But, Flowers beat the deadline.

It was the 1st June and Colossus was working.

And so both Colossus I and Colossus II were in operation

in time for the D-Day landings.

Tunny decrypts made two major contributions to the success of D-Day.

The first was to uncover the entire defensive structure

of the German army.

The most important information

that Lorenz provided for the run-up to D-Day

was the order of battle information,

which give details of the aircraft, the tanks and so on

that were available to the Germans against the D-Day forces.

None of this information came from Enigma intercept.

Even got details of aircraft being refitted

or moved around and so on.

So we had as much information about the German air force

as the German air force itself had.

The other contribution was to eavesdrop

on conversations which confirmed

that the Nazis had fallen for Operation Fortitude,

the fake invasion of Calais.

Hitler had swallowed our deception campaigns,

Hitler was convinced the attack was coming across the Straits of Dover,

and that Normandy was a feint.

These generals, being professionals,

wanted it to be in the Normandy region.

Hitler won out, so we knew that the Normandy region

was less well-defended than it could have been.

As the war through Europe progressed,

the information gained from the Tunny system

began to be used in a more subtle and innovative way.

The effect of this flow of information

helped us to "read" Hitler,

and predict the way he would react and wage war.

In modern terms, it helped us to get inside his head,

something which up until then had been difficult to do,

because Hitler didn't act like a normal military commander.

They had to learn not to think that Hitler would do what they would do,

but to understand how Hitler would actually react in these situations,

and do things that they simply didn't expect him to do.

To hang on to territory when it was completely pointless.

And this was one of the amazing things about the war in Italy,

which people don't really get or understand.

Once the British know from this teleprinter link

that the Germans have decided to keep the front going,

not only do they know how to shape the immediate battle,

but they also realise that they can keep the thing going

for as long as they like.

They can control the extent to which the battle moves forward.

And by doing so, can drain away German resources,

which won't then be used for the main battle, the invasion of Europe.

This is the great irony of the Nazis' love affair

with secrets and machines.

The very devices they trusted to give them total security

allowed the Allies to play Hitler like a fish on a line.

From the beginning, the Nazis were in the impossible position

of having to trust these machines.

Machines which would prove to be an Achilles heel.

The Nazi philosophy led them to distrust people

and to put their trust in machines,

and the problem then is you have to accept the idea

that the machine cannot be broken.

And in fact, all of these machines are vulnerable

provided you approach it in the right way

and that is what the British did.

And the secrets of Nazi Germany, of Hitler himself,

flowed forth because of that.

Unlike here in Britain, where we had one codebreaking organisation,

in Germany, there were seven different organisations

involved in codebreaking.

And they spent a lot of their time just fighting one another -

even, on one occasion, actually physically fighting on the street.

So it couldn't bring together a mass of people

and get the best out of them in the way in which we did in Britain.

Similarly, their ideology meant they were equally ill-equipped

to create their own version of Bletchley Park.

Some people say it's because the kind of people

that worked at Bletchley Park

were just, by German lights, unemployable.

There were gays like Turing, there were Jews,

there were totally disorganised academics,

people who were brilliant but practically dysfunctional.

They just did not fit into the Nazi ethos.

By May 1945, the war in Europe was over,

and Bletchley Park had done its job.

The war cost, on average, ten million lives a year.

This is not counting the wounded and the maimed.

Breaking Tunny at that juncture was pretty jolly important.

For Tutte, and for Flowers in particular,

peacetime would bring a unique set of difficulties.

During the war, Bletchley operated behind a wall of silence.

And thanks to the nature of their work,

that secrecy would remain intact for a long time to come.

Even once the war was over, they still couldn't say.

That was a big issue, and the bosses at the time understood

that that was a security threat, if you like,

so they moved quickly to say to people,

"Sorry, you've got to keep this secret permanently, forever.

"You can't go home and tell your mother or your father

"what you were doing."

And there are many interesting and quite tragic stories

where people didn't, and right into the 1970s and beyond,

parents died without knowing what their children had done.

As for the machine itself, after the war, Churchill let it be known

that Colossus had been broken into pieces.

This was not true.

At least two survived and were taken to the new GCHQ building,

where they were used until the 1960s.

It seems very likely to me that the Russians were using Tunny

in the Cold War period.

As the Russian armies swept across Europe,

they captured numerous German Tunny machines,

and they very probably reconditioned them

and used them for their own communications.

As the Tunny brick was being buried, Tommy was recalled to Dollis Hill.

While he was there, the Americans announced that they had built

the world's first computer, ENIAC, in February 1946.

Already, the true history of computing was being corrupted.

Tommy's suffering in silence was slowly disappearing from history.

As for Bill Tutte, he was awarded a fellowship at Cambridge,

before moving to Canada, where he took up a teaching post

and met his wife, Dorothea.

Bizarrely for a man who had helped defeat the Nazis

with the use of cutting-edge technology,

Bill settled in rural Montrose,

surrounded by German-speaking Amish farmers.

There, he continued to do breakthrough work

at the University of Waterloo,

in a branch of mathematics that was growing in importance

thanks to the rise of computer science.

So he was working in an area of mathematics

that wasn't especially fashionable in the middle of the 20th century,

but it is the mathematics that underlies

much of the theory of computation.

So the importance of his work in the field he helped nurture

became astronomically important,

as the information age unfolded in the late 20th century.

Well, all that was rather nice,

and you see it meant that in the case of unit resistances,

all these determinants were integers,

and therefore if you made the horizontal side equal to the complexity,

all your little squares and rectangle sides,

they all became integers.

Certainly, we're talking about a genius, yes, in many respects.

I think for what he did at Bletchley, he proved it,

and for what he did in graph theory

and related parts of mathematics, he proved it again.

Meanwhile, the story of Colossus was beginning to creep out.

Tommy at last began to receive some recognition.

In 1982, he was invited to talk

at the Museum of Digital Technology in Boston.

When the hostilities commenced in Europe in 1939,

all civil work in Britain had to be subordinated to war work.

In the course of which I was sent to Bletchley Park,

a highly secret establishment some 50 miles north of London,

to take on some top-secret work.

He was still consulting with the MoD as to what he could and couldn't say

and some things were restricted even in the 1980s.

For Tommy, 12 years older than Bill,

the gradual lifting of secrecy came too late.

Although he did live long enough to see his famous machine rebuilt at Bletchley.

He knew that history had treated him badly.

I had the sense that he was weighed down

by all those might-have-beens,

how fabulous it could have been if things had gone differently.

If only it hadn't been for the secrecy.

He also knew - and told me -

that the story was coming out too late for him.

It was too late to make any real difference.

Back in Canada, Bill took the opportunity provided by

his 80th birthday lecture to finally break his silence on Tunny.

And then, if you know the wheel patterns...

INDISTINCT

..you can try the first chi wheel

against the first impulse...

He said that when he finally did tell about it,

finally did speak of it, then it lifted an enormous burden,

and it's hard to exactly say

to the extent to which it may have altered his personality,

the personality that I first met him as.

Outside of a select group of academics, however,

few people realise the significance of these men's achievements.

Bill received the Order of Canada for his academic work,

but he was never decorated by his own country.

He did, however, gain the most important award he could have wished for.

To become a Fellow of the Royal Society

and to sign this charter book, you need to be a leading scientist,

you need to convince your peers that your work is good enough.

So you are refereed in the same way that a scientific paper is refereed.

If you cross that hurdle, Council of the Royal Society

will assess you as being a good enough scientist,

you become a Fellow, and if you get over that hurdle,

then you become a Fellow of the Royal Society

and you sign this very fine book.

It helps if you have a Nobel Prize tucked away somewhere.

In 1987, Bill signed the book.

He joined an illustrious group.

Isaac Newton,

Charles Darwin, Winston Churchill,

and William T Tutte.

Other names in the book are Alan Turing and Max Newman.

Tommy's name was never entered in it,

although one of his many awards

does show the effect of the revolution he helped begin.

When personal computers came in

in the 1980s and '90s, he bought a PC,

tried to work out how to use it and had difficulty,

so he enrolled on a course at the local college

to learn basic information processing,

and he got a certificate, here,

which shows that he passed an introductory course

in information processing,

so he learned how to use programs on a PC like everyone else,

and that was 28th June 1993, when he was 87 years old.

Tommy's only public recognition was to have a road

and an IT centre named after him in his native East End.

The centre has since been closed.

At the end of the war,

Flowers got a leading inventors award for his war work,

and this carried a monetary reward of £1,000,

which was quite a lot of money in those days, of course,

but Flowers being Flowers,

he shared it with his men, and so by the time he had done that,

he'd got about 350 quid for inventing the first electronic computer.

Tommy died aged 92 in 1998.

And Bill four years later, aged 84.

Bill Tutte's memorial

is a simple headstone in a rural Canadian cemetery,

and a lifetime of academic achievement.

Tommy's is slightly different.

My father was cremated and the ashes scattered in the crematorium,

but I think he would have recognised that his main memorial

is at Bletchley Park in the reconstituted Colossus.

As an engineer, to have a working machine

as your memorial is the ideal thing, really.

Hitler ordered this machine himself.

It should never, ever have been broken.

But the minds at Bletchley Park

managed to find ways of breaking it.

And this is an amazing triumph of mind over machines.

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