WHICHEVER WAY YOU LOOK AT IT, the wheel was a great invention. We owe a lot to the cavewoman who first pointed out to her proud mate that his new-fangled "cart", the creation of which he had laboured long and hard over, would be much easier to pull and more comfortable to ride in, if only he would round off the corners on those funny square stone things keeping the cart off the ground. One can only imagine the response from Cro-Magnon man. "What would you know? Stick to your woolly mammoth herding and keep out of my hair!" Which, considering the fashion of the day and the lack of suitably-qualified barbers, would not have been easy.

The usefulness and ubiquity of the wheel struck me yet again recently as I held two pristine examples of 1970s mechanical worldtimer watches in my hands. In my left hand, a Citizen. In my right, a Seiko. Both alike in many ways, and yet completely different in others. Both had the names of major cities around the world printed on a rotatable wheel around the dial circumference. Both had a red 24-hour hand.
  "Nice, aren't they?", whispered the devil's smooth, slippery voice in my ear. "You don't often see them in such good condition. And they're very reasonably priced, too." I felt myself weakening to his infernal temptation.
  "Where did you get them from, John you old devil?" I asked my watchmaker. He grinned a devilish grin and tapped the side of his nose with his finger.
  "Ah, that would be telling. Perhaps you'd like to take them home and do a write-up on them...?" He was really tightening the screws now.

How could I refuse? And later, playing with the city name wheel on each watch, turning it first this way and then that, I thought of another set of wheels I had seen recently, only these were bigger, there were many more of them, and they had helped to shorten the second World War by a couple of years or so. And therein lies another fascinating episode of world history, which I thought I might relate to you. I apologise in advance for the length of this story, but as I delved deeper into my research I kept coming across fascinating snippets and insights of what it was like to live through those days, and why events took place they way they did, and much as I wanted to include everything, I had to force myself to be selective. Even so, there's a lot to wade through!

Of course, if you haven't the time now or just want to skip straight to the watch review, you can just click on the link here. But you'd be missing out on a really good spy story, which has all the necessary ingredients to keep you riveted: greed, money, sex, deceit, cunning, betrayal, more sex, bravery, devotion to duty, and that old favourite, the stupidity of governments and the military. And the best of it is, it's all true. So welcome to the real story of:

T H E   U L T R A   S E C R E T   O F   W W I I

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Following the recent spate of books and of course the movie (strangely enough, entitled Enigma) about British codebreaking activities during WWII, most people will have heard of the Enigma cipher machine used by the German armed forces to encrypt their secret communications, and of the extraordinary work done by the codebreakers of Bletchley Park (located about 40 miles north-west of London) in unravelling them. And most people may be forgiven for thinking that that was all there was to it. But there were many more players in that particular game, over many years and in many countries, as we shall see.

It was Winston Churchill who called the boffins at Bletchley "the geese that laid the golden eggs—and never cackled." This was a reference to their invaluable contribution to the war effort, and the fact that their work remained a well-kept secret. So secret in fact, that it wasn't until 1974, nearly 30 years after the end of the war, that Capt FW Winterbotham was allowed to publish his book The Ultra Secret. ('Ultra' was the codename given to intelligence from deciphered messages sent by the German, Italian and Japanese armed forces.) Winterbotham had been responsible for distributing Ultra intelligence, but not the deciphering of the original messages. So when Gordon Welchman (Head of the Army and Airforce Section at BP) first described in detail how he helped break the German Air Force Enigma in his 1982 book The Hut Six Story, many of his former colleagues were appalled at his blatant disregard of the Official Secrets Act, and the oath of secrecy which he and they had signed. But ironically, it was Churchill himself, and the Royal Navy, who had caused the need for Bletchley Park and its eventual 12,000 strong workforce in the first place........

In the years following the defeat of Germany in WWI, first Churchill (The World Crisis, 1923) and then the Royal Navy (Official History of the World War) published their own accounts of the conflict. Both mentioned the fact that the Allies had routinely broken the German ciphers and had read their secret messages throughout the war. The German High Command (or what was left of it) was horrified to find this out, and set about improving the security of its communications.

What they settled on was an enciphering machine developed and patented by German engineer Arthur Scherbius in 1918. The machine relied on rotatable wheels (also known as 'scramblers' or 'rotors') to scramble messages letter by letter electrically, and to unscramble them again at the receiving end. It was basically an electrical version of the earliest known cryptographic machine, which was invented by Italian architect Leon Alberti in the 15th century. Alberti arranged the alphabet around the circumferences of two copper discs, one being smaller in diameter than the other. By placing the smaller disc on top of the larger and putting a pin through the middle of both, the discs could be rotated relative to each other, thus displacing one alphabet relative to the other. It was then easy to substitute each letter in a message for the one shown on the displaced alphabet, and thus encrypt the message. For example, if the displacement is 3 letters, then A becomes D, B becomes E, and so on. Thus the plaintext message

m  e  e  t    m  e    a  t    m  i  d  n  i  g  h  t     would encrypt to

P H H W    P H    D W    P L G Q L J K W

This simple displacement mechanism is known as a 'Caesar shift' (since Julius Caesar used it to communicate with his generals) or a 'monoalphabetic cipher'. As there are only 25 possibilities for the substitution, it was relatively easy to decode. It was also susceptible to frequency analysis, whereby the ciphertext is examined to see how many times each letter occurs. It is well-known that in English, 'e' is the commonest letter with a frequency of 12.7%, followed by 't' at 9.1%, 'a' at 8.2%, and so on down to 'q' and 'z' at 0.1%. If the ciphertext is long enough (more than 100 letters), frequency analysis can be used to great effect. But Alberti then went one step further, and showed his discs could be used to generate a 'polyalphabetic' cipher by changing the setting of the discs after each letter according to a known key-word. This type of cipher is much less amenable to frequency analysis and is much more difficult to break. It was perfected by French diplomat Blaise de Vigenère who published his Traicté des Chiffres (A Treatise on Secret Writing) in 1586. Vigenère drew up a table (the Vigenère square) in which the first row consisted of the normal alphabet, the second was Caesar shifted by one, the third was shifted by two, and so on until the 26th was a normal alphabet again. A keyword was selected—this could be a word or better still, a phrase—and the message was encrypted by using the alphabet row starting with each letter of the keyword in turn. For example, if the keyword was WHITE, the first letter of the message would be encrypted from the row beginning with W, the second from the row beginning with H, the third from the row beginning with I, the fourth from the row beginning with T, the fifth from the row beginning with E, and the sixth starting from W again. In this way five separate alphabets are used in rotation. So strong was this cipher when used correctly, that it became known as Le Chiffre Indéchiffrable—The Unbreakable Cipher. It remained unbreakable for nearly 270 years, until Charles Babbage broke it in 1854 as a result of a challenge from one John Hall Brock Thwaites, a dentist from Bristol. Thwaites thought he had invented a new cipher, and when Babbage pointed out he had merely reinvented the Vigenère cipher, Thwaites challenged him to break it. Babbage duly did so but didn't publicise the fact; he may have been influenced by British Intelligence to keep it secret as the Crimean War had just broken out, and being able to break the cipher gave the British an advantage over their Russian enemy. (A retired Prussian army officer, Freidrich Wilhelm Kasiski, independently discovered the method and published it in 1863.)

Although the art of cryptography captured the public's imagination in the latter half of the nineteenth century thanks to popular writers such as Jules Verne, Arthur Conan Doyle and Edgar Allan Poe who all incorporated ciphers into their stories, on the professional side nothing much eventuated to replace the now-broken Vigenère cipher. However, the coming of radio at the turn of the century suddenly offered the military previously unheard-of communications capability, but it came at a price. Ships at sea and armies in the field could now send and receive messages instantly, but the enemy could easily intercept these messages via listening stations. The need for secure encryption was greater than ever before. Many systems were tried, but as we have seen, WWI ciphers (particularly German ciphers) were broken on a regular basis. Towards the end of the war the US Army experimented with a cipher using a different random key (i.e. a long, random series of letters, rather than recognisable words) for each message, known as the 'one-time pad' cipher. Unlike the Vigenère cipher this really was absolutely secure. However, practical difficulties meant that it was rarely used in the heat of battle. (One-time pads were later used extensively in WWII by secret agents sending radio messages back to the mother country.)

The cryptological breakthrough came when it was realised the paper and pencil approach hitherto used to devise and break ciphers was no longer effective; advantage had to be taken of modern technology to both speed up and increase the complexity of ciphers by several orders of magnitude. Which brings us back to Scherbius and his encryption machine.

As with many inventions, there were several people working on encryption machines simultaneously but independently of each other. In the US, an American building contractor called Edward Hugh Hebern invented a rotating device in 1917 for polyalphabetic substitution using independent alphabets. In the mid-1920s he started to build a factory to manufacture his machine, but unfortunately for him post-war America was changing from a country with a highly efficient cipher bureau (the so-called "Black Chamber"), to one whose Secretary of State (Henry Stimson) could declare in a new era of openness, "Gentlemen should not read each other's mail". Not surprisingly, Hebern only sold 12 machines and went bankrupt. Hugo Koch in the Netherlands and Arvid Damm in Sweden were two others who lodged patents for similar devices. The government agencies in these countries also showed little interest.

Scherbius' enciphering machine, which he called 'Enigma' after the Greek word for riddle, was originally marketed in two different versions: a basic one for commercial use by finance houses and other large enterprises which were still using fairly unsophisticated codes for their confidential communications, and a deluxe diplomatic version with a printer instead of a lampboard. However, it was an expensive machine to buy, and even though he exhibited it to the public in Berne in 1923 and at the World Postal Congress in Stockholm in 1924, sales were slow. Then, in 1925, the Reichswehr (German Army) bought some machines for testing. They eventually bought over 30,000 of them. The machines used by the military and other government organisations (such as the railways) had scramblers with different internal wiring compared to the few commercial machines which had thus far been sold, further increasing the security of the military machines.

SO WHAT MADE ENIGMA SO GOOD? How does it work? And why was it so hard to crack?
   At first glance an Enigma machine looks very much like a typewriter sitting in a wooden box, with a few extra bits and pieces. The most notable features are a keyboard, a lamp display board, and three large notched wheels or 'rotors' which have the letters of the alphabet inscribed around their circumference. Embedded in each rotor (or 'scrambler') are carefully arranged wires, such that an electric current entering at a point on one side of the wheel exits on the other side at a completely different point, and passes to the next wheel where the process is repeated. Each wheel has the wires arranged differently.
   In practice, when a key (say 'M') is pressed, an electrical current flows into the first (right-hand) rotor, through to the second rotor, through to the third rotor, and onto a 'reflector' wheel which sends the signal back through the rotors again to the lamp board, where one letter (say 'Q') is illuminated. This illuminated letter is the encrypted version of the original 'plain text' letter. Thus the whole message is gradually encrypted, letter by letter. The incorporation of the reflector wheel enables decryption to be an identical process to encryption.
   To increase the number of scrambler permutations, Scherbius arranged for the right-hand rotor to advance one notch at every key press. After one complete revolution of the rotor (i.e. 26 key presses), it turned the rotor next to it by one notch, very similar to a car odometer. In turn, the middle wheel, after completing one revolution, turned the left-hand wheel by one notch. In this way Scherbius achieved 26 x 26 x 26 = 17,576 distinct scrambler arrangements.
   Two further refinements increased the number of permutations or 'keys' significantly: the three rotors were made interchangeable, increasing the number of possible initial settings by a factor of 6, and a 'plug-board' (similar to a telephonist's switchboard) was added between the keyboard and the first rotor, whereby any 6 pairs of letters out of the 26 could be 'swapped'. Later on the German cryptographers increased Enigma security even more. The operators were given two additional rotors, so that by selecting any 3 from the 5 available, the number of initial setting arrangements was increased to 60. Also, the number of plug-board cables was increased from 6 to 10. The number of possible 'keys' or settings then became a staggering 159,000,000,000,000,000,000 or 159 million million million. To put this in perspective, a persistent cryptanalyst who is capable of checking one setting every minute would need longer than the age of the universe to check every setting. No wonder they thought Enigma was unbreakable.

ALTHOUGH THE PROBLEMS INVOLVED in cracking an Enigma message were enormous, the actual processes used in enciphering, sending, receiving and deciphering a message were quite simple.
   Each month, Enigma operators received a new codebook which specified which key should be used for each day. This day-key had three parts: the plugboard setting, the scrambler arrangement, and the scrambler orientation. For example, for the first day of the month, the codebook might specify the following:
   (1) Plugboard setting:    A/L — P/R — T/D — B/W — K/F —O/Y.
   (2) Scrambler arrangement:  2-3-1
   (3) Scrambler orientation:  Q-C-W

To implement this day-key, the operator would set up his Enigma machine as follows:

(1) Plugboard setting:  Swap the letters A and L by connecting them via a lead on the plugboard, and similarly swap P&R, T&D, B&W, K&F and O&Y.
(2) Scrambler arrangement:  Place the 2nd scrambler (rotor) in the first slot of the machine, the 3rd scrambler in the 2nd slot, and the 1st scrambler in the 3rd slot.
(3) Scrambler orientation:  Rotate the scrambler in slot 1 so that the letter Q is facing upwards, rotate the scrambler in slot 2 so that C is facing upwards, and rotate the scrambler in slot 3 so that W is facing upwards.
   The machine is now set up to encrypt the day's messages. The operator takes the plaintext message (e.g. send reinforcements we are going to advance), types in the first letter, and notes which letter lights up on the lampboard. He then repeats this process for the rest of the message, writing down each enciphered letter as it lights up. The resulting ciphertext might look like this:

CQTY FFTP DZLR PGNB SUXA HJRL QKVR OWUI KXIA DPPS LYEJ

(Note that each lettergroup is made up of four letters to disguise short words such as A, THE, MY, AT, TO, etc., and that operators often put in dummy letters to pad out the lettergroups.) The ciphertext is now sent by radio using Morse code to the receiver, who, having set his machine to the same day-key, can reverse the whole process by inputting the ciphertext and writing down the plaintext revealed via the lampboard. (And hopefully avoiding the old British Army joke of the message starting out at the Front as "Send reinforcements, we're going to advance", and arriving back at HQ as "Send three and fourpence, we're going to a dance.")

However, if all the day's messages (and there could be hundreds if not thousands of them) were sent using the same day-key, there was a remote possibility that enemy cryptanalysts could use this vast amount of data to crack the key for that day. So to make things harder for the enemy, the Germans specified that a new message-key would be transmitted with each message, using the day-key to encrypt it. For example, say the day-key specified an initial scrambler orientation of QCW. The operator then picks a new orientation at random for the message-key, say PGH. He then enciphers PGH according to the day-key. The message-key is typed in twice, to provide a check for the receiver. For example, PGH PGH may be enciphered as KIV BJE. (Note that the two PGH's are enciphered differently because the Enigma scramblers are rotating after each letter.) The sender then changes his machine to the PGH setting and encrypts the main message. At the receiver's end, the machine is initially set to the day-key, QCW. The first six letters of the incoming message, KIV BJE are typed in and reveal PGH PGH. The receiver then knows to reset his machine to PGH, the message-key, and can then decipher the main body of the message. In this way the day-key (which is used by everyone sending a message that day) is only used to encrypt the message-key, producing relatively little encrypted text for an enemy to break.

The Enigma machine, when used properly, resulted in very secure communications. However, as a result of its method of construction it had two peculiarities:

• if the same letter is keyed in repeatedly it will encrypt to a different letter each time, and
  
• a letter never encrypts as itself, i.e. A never encrypts as A, B never encrypts as B, etc.

The first peculiarity is a strength in that it combats frequency analysis; the second is a weakness that allowed the use of 'cribs' to assist in decipherment, as will be explained later. Also, the practice of enciphering the message-key twice proved to be costly, as it allowed a brilliant Polish cryptanalyst to peer inside the workings of the military Enigma machine.

INSIDE THE CUSTOMS WAREHOUSE the Customs officer looked at the heavy crate at his feet, then at the piece of paper in his hand, then back at the crate again. The paper was a request from the German Embassy that the crate should be returned unopened to Germany immediately, as it had been sent to Poland by mistake. So he did what any good Polish Customs official would do, and carefully opened the crate. Inside was a commercial Enigma machine. The Polish General Staff's Cipher Bureau was notified, and they in turn called in two engineers from the AVA corporation, a Warsaw-based communications company that worked closely with the Bureau, to examine it. The examination lasted all weekend, following which the crate was packed up again and sent back to Germany. As far as is known, no-one there suspected it had been opened.

The Poles, more than anyone, had a desperate interest in breaking the baffling series of messages which had begun to emanate from Germany and its foreign embassies in 1926. The British, Americans and French had also picked up the transmissions and had tried to decipher them, but secure in their complacency after their victory in the Great War, had given up all hope of making any progress. Only the Poles, sandwiched between communist Russia to the east, and a Germany anxious to regain territory ceded to Poland after the war to the west, had the desperate need for intelligence information.
   Inside the Biuro Szyfrów (Cipher Bureau), the man in charge of deciphering German messages, Captain Maksymilian Ciezki, had had the opportunity to examine the commercial Enigma, but still could not break the Enigma traffic. Unfortunately for him, the military version differed from the commercial one in that the rotor wiring was different. Without knowing the wiring pattern he had no chance of deciphering the German Army's Enigma messages. He then had the idea of employing the country's cleverest mathematicians to attack the problem, which after all was a mechanical one, in a more scientific way. He set up a cryptography course at the University of Poznan, and invited twenty student mathematicians to attend. Three of the twenty showed an aptitude for solving ciphers, and were recruited into the Biuro. They were Marian Rejewski, Henryk Zigalski and Jerzy Rozycki, with the most gifted being the meek, bespectacled twenty-three-year-old Rejewski.
   Rejewski concentrated on mathematically analysing every aspect of Scherbius's machine. He focused on the fact that repetition is the enemy of security: repetition leads to patterns, and cryptanalysts thrive on patterns. The most obvious repetition in the Enigma encryption was the message-key, which was enciphered twice at the beginning of every message. Eventually Rejewski managed to build up a table of relationships involving chains of letters from studying these message-keys, but was still faced with the problem of identifying the correct day-key from the billions of possibilities. It was at this point he had a profound insight. Although the plugboard and scrambler settings both affect the details of the chains, their contributions can to some extent be disentangled. He identified a facet of the chains that was solely a reflection of the scrambler settings, and instead of having to worry about which of the 10,000,000,000,000,000 day-keys was associated with a particular set of chains, he only had to deal with 105,456, which is the number of possible scrambler settings (6 x 17,576). However, he couldn't complete the task until he had more information about the internal wiring of the Army's scramblers, and for that he needed the help of a traitor.

HANS-THILO SCHMIDT drained his coffee cup, set it down on its saucer on the breakfast table, fastidiously wiped some toast crumbs from his mouth, and rang the handbell for the maid. He looked across the table at Charlotte, his wife. As usual she was engrossed in her newspaper, smoke curling up from the cigarette she held in her hand. Gerda, a rather plain but sturdily-built eighteen-year-old with her blonde hair tied into two plaits, entered the room and looked enquiringly at Schmidt.
   "Clear away will you please, Gerda," he said.
   She gave a little bob and started to clear the table. She leant over close to Schmidt as she worked, her ample bosom occasionally touching his shoulder as she reached across the table. He gave her a quick glance and then let his right hand drop down beside his chair, and then he slowly raised it up under her skirt, tracing the inside of her leg. When he reached a certain point she jumped and gave a stifled giggle, and he looked up to find his wife glaring at him. He sighed. Poor Gerda. He had no doubt his wife would now dismiss her, as she had many maids before her, each one being replaced by a more ugly substitute in a vain attempt to stop his philandering. Gerda was no oil painting, but she was young and enthusiastic and the two of them had spent many happy hours making love in the spare room whilst Charlotte was out shopping. There would be row over it, for sure. There always was. Each time Charlotte confronted him over his love affairs, he would try to reassure her by saying she was the only one he really loved.
   "The other women mean nothing to me. I've tried to stop having affairs, but I just can't help myself" he would say.
   Her response was that if he couldn't help himself, she could—by hiring uglier maids. At this he would sigh philosophically and say, "That wouldn't do any good. The uglier they are, the more grateful they are for my taking an interest in them."
   At forty-three years of age Hans-Thilo was still a handsome man. Coming from an upper middle-class background, his circumstances had improved a little when he married Charlotte Speer, daughter of a well-to-do hat-maker, in 1916. Charlotte's mother's family business, C.A.Speer, ran a shop in the Potsdamerstrasse in Berlin, which was the place for smart Germans to go to buy their umbrellas, walking sticks and of course, their hats. But then came the Depression and the shop was forced to close, and with it went the lifestyle he and Charlotte had become accustomed to.
   Hans-Thilo had trained as a chemist, but chemists' jobs were hard to come by in those Depression times of galloping inflation. So he was fortunate when his brother Rudolf, who unlike Hans-Thilo had been retained in the army after the war, was able to get him a job in the German Defence Ministry Cipher Office in Berlin. Here he had access to ciphers made up for the German armed forces. These were kept in a locked safe, but Hans-Thilo was trusted enough to often have access to them. It didn't take a genius to realise these ciphers would fetch a lot of money if offered to another country, and that's what he eventually decided to do. He made contact with the French Secret Service. The French at that time were the leading codebreakers in Europe.

The first meeting took place that Sunday afternoon in the hotel suite of a French Deuxième Bureau spy codenamed 'Rex', in the Grand Hotel at Verviers, a small Belgian town on the border with Germany. At the end of the meeting there was an understanding: Schmidt would bring to their next meeting the best documents relating to codes he could find, and 'Rex' would tell him how much they were worth. The following Sunday the men met again. Schmidt produced two documents which caused a stir in the French camp. They were the manuals explaining how to operate the top secret Enigma machine being used by the German Army. For allowing the French to photograph these, Schmidt was paid 10,000 marks (about £20,000 or US$33,600 in today's money). He was now 'in', and there was no turning back. He apologised for not bringing along a list of the current Enigma settings.

Back in Paris, the cryptographic experts were not so sure of the worth of the documents. The manuals explained the components of an Enigma machine and how to encipher a message, but they did not enable a cryptographer to read Enigma messages. The British experts agreed. The French then offered to show the documents to the Poles, with whom they had a long-standing agreement for military co-operation, and who had earlier mentioned their inability to read the Enigma traffic. The Poles eagerly accepted what the French and British had decided was of no practical use.

As it turned out, Schmidt's documents were pivotal in helping to crack Enigma. Although there was no explicit description of the wirings inside each scrambler, they contained the information needed to deduce those wirings. Thus Rejewski eventually managed to work out the internal wiring of all three scramblers, which enabled replicas of the military Enigma to be built. Exploiting the German practice of encoding the message key twice, he and the other Polish codebreakers, by dint of hard work and brilliant mathematical reasoning, eventually found themselves in the position where they could read Enigma messages the same day as they were sent. They did not, however, inform their French and British allies of this.

For most of the 1930s Rejewski and his team worked tirelessly to uncover the Enigma keys. Little did they know that much of their work was completely unnecessary, because the Chief of the Biuro, Major Guido Langer, already had the Enigma day-keys locked away in his desk. He had been given them by the French, who were still buying information from Schmidt seven years after his first act of treachery. The information consisted of code books, each containing the day-keys for a month. In all there were 38 books, equalling 38 months' worth of keys. Armed with these code books Rejewski could have made short work of the messages for those months. Langer however was thinking ahead; he wanted Rejewski to be able to work out the keys for himself rather than rely on the books, because he could foresee a time when the keys would no longer be available. If war broke out, Schmidt would not be able to continue to meet with Rex, and there would be no supply of day-keys.

MEANWHILE, THE VOLUME OF ENIGMA TRAFFIC had been increasing rapidly, and that together with some alterations to the way messages were sent meant that faster ways of finding the correct keys had to be found. Rejewski responded by inventing a mechanical way of rapidly searching for the correct scrambler settings.
   His invention consisted of an adaptation of the Enigma machine, able to rapidly check each of the 17,576 settings until it spotted a match. Because of the six possible scrambler arrangements, he needed six of the machines working in parallel, each one representing one of the possible arrangements. Together they formed a unit about a metre high, capable of finding the day-key in about two hours. The units were called bombes (in Polish bomby, singular bomba), and to this day no-one is quite sure how they got that name. Various explanations have been given: the machines made a ticking noise like a bomb as they were working; Rejewski got the inspiration for the machine as he was eating an ice-cream called a bombe glacée (in Polish, bomba); the machines dropped weights like an aircraft dropping bombs when the correct wheel position was identified. Whatever the real reason, the name stuck.

In December 1938, German crytographers increased Enigma's security by giving each operator two new scrambler wheels, so that each day they would select three from five, instead of three from three. The number of possible scrambler arrangements thus increased from six (3 x 2 x 1) to sixty (5 x 4 x 3). Not only did Rajewski now have to work out the wiring of the two new wheels, he also had to build ten times as many bombes, each representing a different scrambler arrangement. This latter task was beyond the Biuro's resources. The following month the situation worsened when the Germans increased the number of plugboard cables from six to ten. Instead of twelve letters being swapped before entering the scramblers, there were now twenty. The number of possible keys increased to 159,000,000,000,000,000,000. The Poles could still have continued breaking the Enigma messages if the keys were still available as they had been earlier (courtesy of Schmidt), although they had not been needed due to Polish ingenuity. But Schmidt had now stopped seeing his French contact, Rex, and so the supply of keys had dried up, just when the Poles needed them. The previously routine breaking of Enigma messages slowed to a trickle. Polish intelligence had lost a major component of its information gathering.

During the early part of 1939 relations between Poland and Germany deteriorated, and invasion loomed. At long last the Polish General Staff decided to allow Langer to let the British and French into the Polish Enigma secret, including the workings of the bombe, in the hope that they might be able to carry on the work of decrypting Enigma messages now that the Poles couldn't. On July 24 a meeting was held just outside Warsaw, where to the astonishment of the British and the fury of the French, Langer confessed that he had been reading the Enigma traffic for the past seven years. He also offered them two spare Enigma replicas and blueprints for the bombes. On August 16 one of the Enigma machines was forwarded to London. Two weeks later, on September 1, Hitler invaded Poland and the war began.

SINCE BEFORE THE FIRST WORLD WAR, the main British code-breaking work had been carried out in the Royal Navy's Cipher Office, originally based in Room 40 of the Admiralty, London. It was here in 1917 that the famous encrypted 'Zimmermann' telegram, sent by German Foreign Minister Arthur Zimmermann and asking Mexico to join Germany in going to war against the then neutral United States, was cracked. It was staffed with a strange mixture of linguists, classical scholars and crossword addicts, on the basis that people with these skills were the best at cracking codes. And indeed, they had many successes.

(The idea that crossword addicts made good cryptanalysts persisted for many years. In 1942, as part of a recruiting drive, the Government Code and Cipher School (which gradually took over from 'Room 40') anonymously placed a letter in the 'Daily Telegraph' challenging readers to complete a crossword in under 12 minutes. The 25 readers who responded to the challenge were invited to Fleet Street to sit a crossword test. Five of them completed the crossword in the time allowed, and another had only one word missing. A few weeks later all six were interviewed by military intelligence and recruited as codebreakers at Bletchley Park.

   Do you think you have what it takes to be a codebreaker? Click here to see the crossword they had to do in under 12 minutes, and you can try it for yourself.)

With the looming onset of war, it became obvious that a much larger staff would be needed than could be accommodated in the suite of offices still known as 'Room 40' in the Admiralty, or the offices of the newly-formed Government Code & Cipher School (GC&CS) located at Broadway, near St James's Park in London. What was needed was a location outside London (to be safe from bombing), and yet close to major lines of communication. MI6 officers scoured the countryside, and eventually found a rather forbidding Victorian Tudor-Gothic mansion for sale at Bletchley, Buckinghamshire, about 40 miles north-west of London straight up the A5 (the old Roman road known quaintly as Watling Street). Actually, calling it Tudor-Gothic in style does the mansion an injustice, as there were no fewer than 17 different recognisable architectural styles incorporated within its stout walls. (Don't forget, the mansion was built at a time when no-one had heard of planning approvals.) The mansion was set in large, park-like grounds, which afforded plenty of room for expansion and also excellent security and freedom from nosy neighbours. It was at the junction of major road and rail connections, and quite close to both Oxford and Cambridge Universities.
   And so it came to pass that one weekend in late August 1938, "Captain Ridley's shooting party" descended on Bletchley Park, ostensibly for a weekend of huntin', shootin' and fishin'. They even brought with them one of the best chefs from the Savoy Hotel to cook their food. In reality, the shooters were senior codebreakers from the GC&CS, assessing the suitability of BP as the new home for the School. The "shooting party" was a cover to avoid arousing the locals' suspicions.
   Bletchley got the thumbs up from the assessors and from then on was known by its codename, 'Station X'. The 'X' didn't mean 'secret', although BP and the work that went on there was one of the best kept secrets of the War: it was the Roman numeral for 10, as Bletchley was merely the tenth property MI6 had bought for communications purposes. (Just to make things more confusing, there was also a chain of monitoring stations known as 'Y' stations across Britain and in some overseas countries. These stations had huge aerial 'farms' and were Britain's 'ears', listening in to the enemy's radio messages. Thousands of wireless operators tracked the enemy radio nets up and down the dial, carefully logging every morse letter or figure. These messages were then sent back to Station X to be decoded.)
   As the number of codebreakers employed at Bletchley grew from the original 200 to many thousands, makeshift wooden huts were constructed in the grounds to accommodate them. These were known pragmatically as "Hut 3, "Hut 6", "Hut 8", or whatever their number was. Each hut carried out a particular activity, and they tended to work in pairs. For example, Hut 6 specialised in German Army Enigma, and passed the decrypts to Hut 3, where intelligence operatives translated the messages and attempted to piece together the information. Hut 8 specialised in the Naval Enigma, and passed their decrypts to Hut 4 for translation and intelligence gathering. (It should be realised that there were many military and non-military radio networks, and they mostly worked with different day- and message-keys for greater security. Some Enigma networks were easier to crack than others, generally because of careless operator or procedural errors. The Naval Enigma however remained the toughest to break throughout the war, due to a move to 4-rotor machines and stricter operator procedures. Apart from Enigma there were also other ciphers that had to be broken, such as the Offizier cipher, the Lorenz cipher in which Hitler corresponded with his generals, and the Italian and Japanese ciphers. All this work was done at Bletchley Park. More of this later.)

Thanks to the pioneering work done by the Poles, and from it the realisation that Enigma could be broken and was not undecipherable as originally thought by the Allies, the BP codebreakers set to with a will and achieved some early breakthroughs. Also following the Polish example, the recruiters began trawling through Oxford and Cambridge Universities, looking for likely mathematicians and scientists to work at BP as cryptanalysts alongside the linguists and historians. Although many bright young men (and some women) were signed up, there was one 27-year-old whose genius was to make him a legend among his peers. His name was Alan Turing, and it is quite likely there was not another person living in the world at that time who could have done what he did.