The Lost World of Bletchley Park

by Sinclair McKay

  Local Bletchley women also volunteered for work at the Park. The establishment needed a number of support roles – from canteen workers to messengers – but the level of intense secrecy remained the same whatever the work.

  Wrens billeted at nearby Wavendon Manor, a handsome 18th century house. According to veteran Molly Morgan, the place was reputed to have the inconvenience of a haunted bathroom.

  Later, Mimi graduated to working in the main house, in the suite of offices used by the Bletchley Park directorate. It was there that she worked much closer under the tutelage of Doris Reid. Indeed, many years afterwards, the two women managed to get in touch once more, and Mimi became good friends with the boss she once feared.

  The Official Secrets Act also covered staff such as chauffeurs and canteen workers. All these different people and occupations gave the Park not only a distinctly youthful atmosphere, but also one that was not dominated by a single class; for all the Fair Isle-jumpered codebreakers and the debutantes with voices like cut glass, there were also thousands of young women and men drawn from more down to earth backgrounds. The social jumble was found fascinating on all sides: the debutantes beguiled by the energy and confidence of the local girls they saw at the village dances; and the grammar school-educated codebreaking men mesmerised by women who, as one veteran said, they would only otherwise have read about in the upmarket gossip columns of newspapers.

  ABOVE AND BELOW The intense pressure could induce nervous breakdowns; but many Wrens hailing from industrial towns found the countryside around Bletchley refreshing and conducive to long walks.

  ABOVE AND BELOW Wren Ruth Bourne recalls how she guessed what sort of work she was being drafted in to – she had read enough thrillers, she said, to recognise a codebreaking operation when she saw one.

  Chapter Five

  THE MACHINES THAT CHANGED THE FUTURE

  The shape of things to come: an early Colossus machine in 1944. It was set up, wrote codebreaker Jack Good, by means of ‘Boolean plugging and toggle switches’ – in other words, the forerunner of what was to become computer programming language.

  The four-rotor naval Enigma caused a terrible black-out in Hut 8 for months in 1942; the horrible complexity of the earlier models was multiplied many times over.

  For a device designed to take language apart and scramble it into impenetrable chaos, the Enigma machine was a remarkably neat-looking construction. Made of wood and brass and Bakelite, it had a standard German keyboard layout, plus a lamp board with letters that were illuminated from beneath, slots for medal-sized bevelled wheels and, down at its front, what looked like a miniature telephone switchboard, with small plug-holes and tidy wiring. It was perfectly portable; the machine came in a wooden case and could be very quickly packed up. It looked like the sort of machine one might find in an accounting office, or even perhaps on a newspaper editorial floor, but it was diabolical in its ingenuity.

  Unlike other encoding systems, which might rely on simple letter substitution – an ‘X’ for an ‘A’, for instance – every time a key of Enigma was pressed, one of the brass rotor wheels would move, and the ‘A’ might next time be substituted with a ‘Q’, lit up on that lamp board. The weakness of letter substitution systems is that the most commonly used letters, such as ‘E’, might be spotted even in code by means of their frequency in a string of coded letters. The Enigma eliminated that comfort. You could take a simple sentence in plain language and throw it into an infinity of randomness, with a potential for millions upon millions of letter combinations. This machine was the nightmare challenge faced by the mathematicians of Bletchley Park.

  Yet even before the war, there had been extraordinary – and highly secret – successes in attacking it. The Enigma itself was patented in 1918 by Arthur Scherbius. It had been intended as a commercial encryption device; in the mid-1920s, there was a sales brochure to promote it. ‘Ciphering and deciphering has been a troublesome art hitherto,’ it read, this document aimed at business leaders and financial houses. ‘Now we can offer you our machine “Enigma”, being a universal remedy for all those inconveniences.’

  As one of the three Poles who first cracked Enigma in 1932, mathematician Marian Rejewski never got full credit in his lifetime. He died in Warsaw in 1980 but was buried with military honours.

  The sales staff were also quite aware of its potential for military use. In 1926, the British were offered a version. They turned it down. The German Navy, however, decided to pick it up. They swiftly made a few alterations to ramp up its security and by the end of that decade, Enigma was being rolled out across what was left of the German military after the Treaty of Versailles. Even as early as 1929, there were those in the Polish government who were sufficiently concerned by this development to try and take precautions against it. Polish intelligence began a trawl for gifted mathematicians and three in particular were to make their name, attaining a sort of cryptological immortality: Jerzy Rozycki, Henryk Zygalski and Marian Rejewski.

  It was Rejewski himself who said, ‘Wherever there is arbitrariness, there is also a certain regularity. There is no avoiding it.’ This sense of mathematical and philosophical openness was to lead him and his colleagues to some remarkable and invaluable successes. By 1932, they had broken one of the early Enigma systems. And as the decade wore on, with the Germans (and after 1933, the Nazis) working harder on constantly updating and improving the Enigma device, Rejewski and his team, with the help of some extraordinary espionage work, fought hard to keep pace. It wasn’t always possible. The Germans had by now introduced the ‘stecker board’ to the Enigma; a further complication, involving wiring plugged in different ways according to each set-up of the machine. But by the summer of 1939, with the frightening noise of increasing German aggression carrying across the Polish border, there was a meeting in a forest near Pyry between the Polish mathematicians and Bletchley’s senior cryptographer Dilly Knox, where they managed to pass on invaluable information about the way the machine was set up. Although Knox was apparently infuriated that the Poles had beaten him to the solution he had spent the last few years searching, Bletchley Park was given a terrific head start.

  The Poles had also been working on methods of speeding up the checking of different combinations: there were the Zygalski sheets and the bomba machines. The sheet method was both ingenious and tortuously complex, very basically involving special sheets of perforated paper with grid square patterns of four squares of 26 by 26, and letters, all arranged on a light box, to calculate via painstaking mathematics possible Enigma wheel orders. The bombas (the term meaning ‘ice cream’) were not wholly reliable machines, the idea of which was to run six sets of Enigma wheels simultaneously in order to search for repeated enciphered letters. They were considered less effective than the Zygalski sheets – but the basic idea of the bombas, the notion that machines could be made to do some of the heavy repetitive checking tasks, was taken up by Alan Turing and Gordon Welchman and refined into Bletchley’s bombe machines. It was the crucial addition of an electrical ‘diagonal board’ – which in a symbolic sense rather mirrored the German innovation of the stecker board – that made this technical approach much more feasible. Cryptology was moving fast towards a wholly mechanised age. These bombe machines alone could not actually crack Enigma – but if fed ‘cribs’, or head starts, such as repetitive weather reports, or even friendly greetings between different German commanders, they could then power through thousands upon thousands of different combinations at a speed that no number of humans could get near. Enigma messages – from whatever part of the German war machine – were generated by dedicated operators working with code-books and pre-arranged settings that would change every 24 hours. The encrypted letters, illuminated on the lamp board, would be noted down by the Enigma operator, then transmitted by Morse code, the scrambled letters arranged into groups of four or five. It was those groupings that the codebreakers would then be examining after these messages were intercepted: column upon column of random letters in
uniform groups. It’s easy to see now just how daunting the prospect was. But the Poles, together with a French contingent and the British, saw another tiny sliver of light, another slender means of perhaps getting a firm foothold into the machine. One weak point in the Enigma encoding system – if such an esoteric aspect of the system might be termed ‘weak’ – was the fact that the machine would never encrypt a letter as itself. In other words, A would never become A. For anyone else, this aspect of its workings would be of little assistance. But the mathematicians and classicists combined were relentless in their attacks upon the entire structure of Enigma, and any means by which entry points might be forced.

  ABOVE AND BELOW Once an Enigma key had been broken, ciphered messages were fed through Typex machines, to produce the clear German text.

  The staggering success of the whole operation – the sheer weight of messages intercepted, decrypted, translated and analysed – is illustrated by the fact that they ran out of shelf space for the fast-expanding cross-referencing card index files and had to line them up on the floor.

  The top secret workshop in Letchworth where Harold ‘Doc’ Keene and Oliver Lawn oversaw the manufacture of the revolutionary bombe machines in 1940.

  The first two bombe machines – built by Harold ‘Doc’ Keen and the British Tabulating Company at Letchworth – made their Bletchley debut in the summer of 1940. Prior to this, Enigma had been broken by hand, as it were, thanks to such leaps of insightful genius as the Herivel tip. Young mathematician John Herivel had, after the end of a long shift, returned home and set to imagining the German operators of Enigma. He imagined these straight-talking men, possibly using the names of their girlfriends in message preambles, or even jocular swear words. Herivel also imagined how they might set up the Enigma machines on each new day, and how they could be tempted to take shortcuts. Such shortcuts might be detected, and thus open up an entire trove of messages. The bombe machines could only be effective exactly because of this genius flash of psychological insight: once a shortcut or repetition was confirmed, the bombes could then set to work in earnest.

  Alan Turing’s revolutionary bombe machines clattered through thousands of code combinations at top speed with drums rotating ceaselessly.

  At the Eastcote out-station, different bombes were allocated to separate territories.

  ABOVE AND BELOW But they had to be tended night and day by Wrens, standing by to re-set them.

  An early American Hollerith machine, the type used to count the 1890 census – the ‘punch card’ system was later specially adapted for Bletchley’s use.

  The bombes were large cabinets filled with rotating drums, and the back of each machine featured intricate wiring. Wrens worked throughout the night, keeping watch as the machines worked through their menus, and taking note whenever a bombe reached a ‘stop’ on the correct code-setting. It was often quite physically trying tending to the needs of these vast contraptions. The wiring had to be adjusted with tweezers and when there was a room full of the machines, some Wrens found the incessant noise quite difficult to deal with, though veteran Jean Valentine recalled for her own part that it wasn’t actually all that bad – more like the ‘clickety-ticking’ of knitting, as she put it.

  In 1940, the first two bombes had been conveyed to Bletchley under a shroud of utter secrecy (and in unostentatious lorries – the authorities did not want to excite curiosity by making a huge security song and dance of them). Soon thereafter, the numbers of these machines multiplied – some 210 bombes were built in all – and veteran Wrens now look at them with what might be described as mixed feelings. By the end of the war, in 1945, Harold Keen had received an OBE for his war work, for which he was warmly congratulated by his Hut 6 friend and collaborator Oliver Lawn. After the end of the war, the machines at Bletchley Park were destroyed.

  Another crucial – though oddly less celebrated – machine system in use at Bletchley Park was the Hollerith machine. This was an evolved version of a 19th-century innovation, invented by Herman Hollerith and used rather impressively to collate the 1890 US census. It was a punched-card system, much favoured by retail businesses such as department stores, that was adapted for Bletchley’s purposes, first to act as an intelligence index, but also to help the codebreakers mechanically reduce the number of potential Enigma wheel settings that they would have to check. Unfortunately for the operators, whereas the bombe machines had at least a sort of hypnotic fascination about their clickety-ticking function, the Holleriths were a little more utilitarian. One veteran recalled being bored to tears as she learned how to punch information on to special cards, adding that the process became a little less tedious when it was automatic. The machines were used to look for ‘four-letter repeats’, in conjunction with platoons of linguists. There were various dizzying stages of information storage, running from the Collator, to the Reproducer, with intelligence being saved on master cards. So even though it was some distance behind Alan Turing’s revolutionary theories concerning machines that could be made to ‘think’, the Holleriths were still an early means of saving data mechanically.

  Throughout those years, encryption technology was moving fast; several years into the war, the Germans were now also using a system termed Lorenz, known at Bletchley as ‘Tunny’ or ‘Fish’ because of its other German name, Sagefisch. These machines were described as ‘non-Morse teleprinters’ and worked with tape, using binary digits as the means of encoding messages. Lorenz was not a portable system and it was mainly intended for use by German High Command, to communicate directly with the headquarters of their field marshals. Whereas the Enigma messages – often sent from the field of battle – tended to be tactical, the Lorenz traffic was more about long-term strategy. To find a way into it would be a prize beyond value. Brigadier Tiltman was the first to do so, rather staggeringly by hand. Yet as with Enigma, the Germans kept on adding extra secure features to the apparatus and soon only a technological way into the code would be possible. Professor Max Newman and talented figures like W. (Bill) Tutte, and a department of the General Post Office situated in the London suburb of Dollis Hill, set to work. Their first answer to the Lorenz conundrum was a machine that they called – with an element of self-deprecation, referring to his brilliantly comic drawings of mad inventions – the Heath Robinson.

  In fact, this machine – a mass of wires and spools and paper tape – which made its debut in April/May 1943, was a brilliant stepping stone; using the new technique of photo-electronics, it was capable of reading 2,000 characters a second. It worked with closed loops of tape which were pulled through the machine via sprockets and pulleys. Unfortunately, it also had practical drawbacks, including a tendency for the paper tape to tear. Veterans recalled that, as a system, it was both maddeningly delicate to operate and fantastically frustrating when it quite frequently broke down. But it did prove that Professor Newman had hit the right principle; what was needed was a rather sturdier construction. In other words, this was not just a problem of codebreaking; this was an engineering challenge. In that Dollis Hill GPO unit was a very talented man called Tommy Flowers; born in East Ham, educated at night school. Although there was some resistance from Gordon Welchman, who clearly did not quite trust this non-Oxbridge figure, Flowers combined his wits with Max Newman. The Flowers solution was a machine that would be called Colossus. Although not strictly a computer, it was the very clear antecedent. Before the war, Tommy Flowers had been working on telephone technology – he brought in electronic digital equipment that used huge numbers of vacuum tubes, an idea that he saw could be pressed into service elsewhere. The tapes of the Heath Robinson were now largely replaced by electronics: the first Colossus contained around 1,500 thermionic valves. It could read 5,000 characters a second. The later version had around 2,500 of these valves and could read even more quickly. Flowers realised that the most practical way to avoid this construction breaking down was very simply to never switch it off. There had been some objection to his procurement of so many valves; the furious me
mos in the archives now point to a period of great inter-departmental tension. But when Colossus started helping to crack messages from high-ranking German commanders to the office of Hitler himself, Flowers was triumphantly vindicated. In March 1944, almost as soon as it had started operation, Colossus managed to crowbar its way into correspondence between the Fuhrer and Gerd von Rundstedt, the Commander in Chief in the west. As we shall see in chapter nine, the impact of this upon D-Day was almost incalculable.

  The later years of the war brought more complex Nazi codes – and still more complex technology to crack them in the form of the Colossus.

  The vast – and crucial – Bletchley card file index. Drawn from German decrypts, the aim was to catalogue and cross-reference all names, technical terms, operational jargon, even personal family information. It was absolutely key to the success of breaking into so many codes.

  Visually, the Colossus was a beguiling, if complex creation. It was tall enough almost to touch the ceiling and wide enough to nearly fill the room. On one side, a bank of switches and tiny lights, flashing red and white; in the middle, further switches, a plug-board and, below this, a teleprinter that would chatter into life when the correct setting for a code had been found. To look at the brilliant recreation at Bletchley Park now, you are irresistibly put in mind of old Quatermass films, or any number of quaint 1950s British science fiction epics. On the other side of this construction was the part that the operating Wrens must have dreaded most: multiple suspended reels, upon which ran the remaining paper-tape component. This would run at 30 miles per hour, and was infuriatingly prone to snapping and exquisitely hard to manoeuvre into position so that it would run smoothly at the start of every set-up.