The Secret Lives of Codebreakers

by Sinclair McKay

  In terms of security, this was obviously invaluable. As Sheila Lawn’s landlady indicated, it was obvious to the people of the town that the Park was a secret establishment, and swarming with scientists. But to stifle the urge to discuss, or speculate, seems to have become endemic.

  As Mimi Gallilee explains, what now seems startling would have come much more naturally back then. At the start of the war, it was not merely the ubiquitous “Careless Talk Costs Lives” posters; road signs and railway station signs were taken down as a means of confounding potential spies and potential invaders. It was widely understood, whether in the forces or as a civilian, that one should discuss no more than necessary.

  Given that, says Mimi Gallilee, one couldn’t occasionally help wondering what was going through the heads of the townsfolk. “What I marvel at is: what were the people who lived in Bletchley thinking? I don’t ever remember anyone ever saying to me ‘What do you do there?’ So I began to wonder. What on earth were they thinking about? What did they think was going on in the Park?

  “Nobody said anything. The Bletchley inhabitants had no reasons to carry any secrets about with them. So it wasn’t duty.”

  Perhaps there is a slight class factor: that of the folk in the big house having automatic precedence over the townspeople overlooked by the estate. Regardless of their youth, the largely middle-class intake of recruits to Bletchley Park were of a higher social station than the townsfolk. And the townsfolk simply had no business asking them about their affairs.

  Even though households throughout the country were presented with so many extra tenants, there were some who were able, by dint of special pleading, to keep their houses and bungalows free of interlopers throughout the war. In general terms, the system involved inspectors first visiting likely properties, and asking the occupants what room they could provide, if any. The more quick-witted, privacy-loving homeowners became adept at spinning yarns concerning elderly relatives and available living space. There does not seem to have been any such reluctance at Bletchley.

  As staffing levels at the Park ballooned, living arrangements were provided at the stately home of Woburn Abbey, among other locations. Woburn was quite a different proposition from that of the Bletchley billet. But one of the most evocative—and pivotal—of all billets was that occupied by mathematician John Herivel. In his memoir, he wrote:

  I returned each evening to my billet close by in one of a long line of terraced houses in the road sloping down from the level of the Park towards the railway bridge. I had been given a sitting room in the front part of the house, and when the landlady— alias the lady of the house who had been required by an all-powerful wartime government to give ME board and lodging in HER house—had cleared away the supper dishes, said good night—I hope I stood up as she did so—and closed the door, I was then totally cut off from the outside world except for the occasional faint Proustian sound, through the tightly drawn curtains, of the shuffling feet of some lost soul toiling up or down the hill in the deep snow outside—for the winter of 1940 was an exceptionally severe one.

  As for me, each evening I was soon installed in a very comfortable late Victorian or early Edwardian armchair before the fire, always hissing and spitting as it really got under way, backed up by a full scuttle of coal, enough to see me halfway through the night.5

  It was in this exact room that John Herivel was to make the psychological leap that helped to break the Enigma codes.

  8 1940: The First Glimmers of Light

  So, with practically nothing in the way of ceremony—or indeed, in some cases, of more than rudimentary training—the young recruits squared up to their extraordinarily complex, grueling, grinding tasks. As Keith Batey has recalled, the nature of the work often had very little to do with mathematics and everything to do with patience and concentration.

  The working day would be split into three shifts: 4 p.m. to midnight, midnight to 8 a.m., 8 a.m. to 4 p.m. It was the Air Section, under Josh Cooper in Hut 10, that started the 24-hour watch system quite early on, and the routine was quickly replicated across the establishment. Among codebreakers—and later, the Wren bombe operators—the shift most disliked, quite understandably, was midnight to 8 a.m.

  But the intention was to speed up the decoding and translating work. With the enemy’s code settings being changed on a daily basis, the amount of signals traffic to be worked through could not be delayed in any way.

  Keith Batey remembers that the nature of the work was not almighty intellectual effort: “I wouldn’t describe the work as hard slog. More tedious,” he says. “In fact, the work I was doing to begin with in Hut 6 didn’t even require a mathematician. I told Gordon Welchman that any of the girls could do it.”

  Sheila Lawn equally recalls the unromantic and often unexciting nature of the tasks before her. “I just did what I had to do. It wasn’t exciting. I got these messages, I translated them, I decoded them, and simply got through them. They got a lot in. From the radio stations and gun emplacements along the Dutch, Belgian, and French coasts. And some in the Mediterranean, but I never distinguished that, and didn’t ask too many questions. It was sightings, weather reports, sightings of ships, sightings of aircraft, anything peculiar.”

  For the Honorable Sarah Baring, the notion of a work ethic was already firmly in place before her arrival at Bletchley, thanks to her stint at the plane factory near Reading. Physical labor was one thing, though; the concentration required for translating duties at Bletchley was another.

  “It was the hours,” she says. “You were translating German decrypts. And you really got to know how to do them pretty quickly. If you had the lingo, that is.” The shift system also took a little getting used to, as she recalls: “If you turned up for work in the day, hopefully night shift had got through a bit of the messages. It depended on what was going on. There was always plenty to do.

  “But night watches were hell,” she adds. “You do get a bit tired, but then suddenly you’re woken up by a signal that is so important that you sort of become alive again. It’s not just routine. You suddenly get terrifically excited about where such and such a U-boat is, or where the Graf Spee is. You’ve got something really worth it.

  “And the sleep patterns! They were awful, because we changed every week, from day watch to night watch. That was hell. But everyone did it, of course. Soldiers, sailors, everyone.”

  No one in the huts, according to Ruth Sebag-Montefiore, looked their best after so many nocturnal hours of ferocious concentration. “Individually, these backroom boys, with their original minds and brilliant brains, could be described as interesting looking,” she recalled. “Seen collectively, as they poured out of their huts for a breather or en route to the dining hall, with their gesticulating arms, unkempt hair, and short-sighted eyes peering through thick spectacles, they looked like beings from another planet.”1

  The actor Sir Anthony Quayle—who according to some spent a little time himself at Bletchley later in the war—was deeply, and helplessly, in love with a married actress called Dorothy Hyson. At that time, Hyson was a byword for theatrical West End glamour. The night work that awaited her now was of a different order. Hyson had been summoned to work at the Park while Quayle was out in Gibraltar serving with the forces. Once, when he was on leave, Sir Anthony recalled, “Dot, the essential reason for my return to England, was not even in London; she had gone to work as a cryptographer at Bletchley Park. I went to see her there and found her ill and exhausted with the long night shifts.”2

  Many decades on, cryptographer William Millward found himself pondering the side effects of the punishing shift system. He wrote:

  We worked in shifts on a pattern allegedly recommended by the medical authorities, its aim being to avoid painful changes in the circadian rhythm. It meant in practice destroying this rhythm… I worked these shifts for two and a half years with one week’s leave a year, and have sometimes wondered whether working thus, with all the excitement and dedication which it involved, was perhaps
a cause of the bad insomnia which hit me some dozen years later.3

  Some female veterans recall that, occasionally, a night shift in a hut could have an uncomfortably quiet, “spooky” quality. Then there was the difficulty of moving around outside in the thick darkness, with few effective torches. One recalls that she found herself subconsciously memorizing where the potholes in the roads were.

  “I have a memory of looking out of the first-floor window of the house,” says another veteran, “just as a night shift was switching over. Some people would be coming in to start work, others going home. And I seem to have this image, of seeing, down by the lawn and the lake, all these people, milling around in the dark.”

  Sheila Lawn, however, recalls the upside of the system. “Because we were all young, we were very adaptable. I think now the shift system would be a big shock to my system. But no, we were very adaptable, we just accepted this. And there were advantages and disadvantages. A more flexible day. Sometimes you had to work at night, of course, but you had part of the day to yourself.”

  Another veteran is equally phlegmatic: “When you changed rota, your sleep pattern would change and that gave you an awkward day or two. But this is how it was.”

  But it was not just a question of sleep. The ever-pressing need for 100 percent accuracy meant that the pressure in the small hours could be unusually intense.

  Keith Batey offers an insight into the intricate yet repetitive nature of the work, talking of the simple-sounding yet fearsomely complex “rodding” system invented by Dilly Knox. “They assumed that there was a word likely to appear in the message. Six or more letters. And you could select places worth looking at by checking for what we called ‘clicks.’ In other words, you set the assumed plain letter against each section of text and look for settings on Dilly’s rods where you got the same twice—charts were made to pick out all the ‘clicks’ quickly. When you got a double ‘click,’ you set the rods up to see if it would work. Very often it did—you didn’t set out to work on each code seventy-eight times.”

  As well as Dilly Knox’s system of rods, there was the “Zygalski sheet” system devised by the Poles who had originally broken into Enigma, and updated and modified at Bletchley by John Jeffreys, Alan Turing, and Gordon Welchman. The updated versions were known as “Netz” or Jeffreys Sheets.

  Of great help to Bletchley was Dilly Knox hitting upon the principle of what were termed “cillis.” These were defined by Sir Harry Hinsley as “procedural errors by Enigma operators combining (1) a recognizable instead of random choice of message setting, and (2) failure to alter the wheel position much, or at all, before sending a message.” Sir Harry added that this insight was thought to have been named after a German operator’s girlfriend, called Cilli. The operator, using his girl’s name as a message setting, had shortened it to “Cil.”

  On top of this, there had been, according to Alan Stripp, another chink in Enigma’s armor: the “indicator setting.” After following instructions for that day’s wheel order, ring-setting and cross-plugging, the German Enigma operator would turn the three wheels to a random starting point. Then, as part of the preamble to the messages the operator sent, he would twice key in “his own randomly selected choice of text-setting,” as Stripp noted.4 This choice might be FJU. He would then tap the setting out again as confirmation, and it would appear as encrypted letters, say PORCDQ.

  “The operator had to give an indicator for the chap at the other end,” says Keith Batey. “But because of the possibility of Morse error, it was repeated, so you got two of these three-letter things. So that you knew that there was a repeat.”

  Once Bletchley had worked out the nature of the six-letter preambles, they instantly provided a slender means of working back through the rest of the code by days and days of calculation (though of an intensity that would still be utterly beyond most). “But then,” adds Mr. Batey, “the Germans suddenly began to realize that this was bad.” Once the Germans became aware that the practice—originally instituted for extra security—ironically made their communications very much less secure, they put a stop to it in May 1940.

  And this had only ever applied to military and air force traffic; the German naval Enigma was never so straightforward to catch out. From the start, it was a very great deal tighter and more labyrinthine in its theory and use. Its operators had far less personal leeway, and thus, the chance of the operators making mistakes were virtually eliminated.

  The work was thus not simply a matter of clever young people in Fair Isle sweaters gazing blankly at apparently random letters; it was these same young people using tiresome though necessary means to test and test and test again, against such regular messages as enemy weather reports and call-signs, the language of which were presumed straightforward and repetitious enough to help produce some kind of a crib.

  In the coming months, when successful attacks upon Enigma had resulted in a specific codebreaking methodology, the huts were to become extraordinarily intense places to be, not only for cryptographers but also for translators. “When the codebreakers had broken the code,” explained Peter Twinn, “they wouldn’t sit down themselves and painstakingly decode 500 messages…by the time you’ve done for the first twenty letters and it was obviously speaking perfectly sensible German, for people like me, that was the end of our interest.”5

  The messages would then be passed on to the Machine Room, in which British Typex code machines had been rigged up to act as Enigma machines. Here, operators, normally women, would set the machines up using the decrypted keys, sit down, and start typing. If the code was correctly cracked, what they typed would appear in German.

  Then there was the matter of translation. As historian and codebreaker Peter Calvocoressi recalled:

  The Watch in Hut 3 sat around a horseshoe table. Their function was to translate the deciphered Enigma material from Hut 6, interpret it and transmit it abroad. What the Watch received was a stream of slips of paper the size of an ordinary Post Office telegram, or on two or more such bits of paper.

  The letters were in five-letter groups and ideally they made German words. A dozen people sat around the semicircular table with the head of the Watch inside the semicircle and facing his colleagues who were scribbling away or scratching their heads. They all knew German as well as they knew English.

  Schoolmasters were ideal for the job, as they were meticulous. If not satisfied, they would throw back a translation at even an eminent professor. It reminded me of Chief Examiners at “A” level who would send back scripts to an Assistant Examiner to re-mark.6

  Once the messages had been successfully decoded and translated, there was the organizational horror of the cross-referenced card system to be faced. And this, it seemed, was a problem that required a rather more upper-class sort of girl to take on. Oliver Lawn recalls: “The Intelligence people could of course read the messages. They could decide what information, if any, to pass on to whom. And they were supported by a huge card index.

  “Let’s take as a random example someone called Bruno Schmidt. As the subject of a previously decoded message, he would have been entered into the card index. And from this, one could pull him out in the future when he turned up in other messages.

  “One could ask: ‘Ah, yes, this chap is a rocket chap, he’s to do with rockets. He is being moved from A to B. Why?’ And this information came about because of the accumulation of the card index. That was the information side. Now the index used to be put in a section which was locally called ‘The Deb’s Delight.’

  “This,” Mr. Lawn continues, “was because the debutantes, and ladies from high society, were regarded as suitable for doing this indexing work. Ladies—a few with rather modest brains—very well connected, and very loyal and security conscious.”

  As a result of the “sheet” system and the “cillis,” and thanks to the crucial involvement of the Polish codebreakers, Bletchley Park’s first break into current military Enigma traffic—as opposed to old messages—came in Janu
ary 1940.

  Alan Turing had been sent to Paris to confer with the Poles about such matters as wheel changes in the Enigma machine, taking with him some of the Zygalski sheets. In those few days, they managed to crack an Enigma key via this method. One of the Polish mathematicians, Marian Rejewski, remembered his dealings with Turing: “We treated Alan Turing as a younger colleague who had specialized in mathematical logic and was just starting out in cryptology.”7 At the time, he was not aware that Turing had quietly been making some astounding cryptographical leaps off his own back. Nevertheless, the Polish contingent based in Paris—even with their scantier resources—were still brilliantly helpful to the Bletchley operation.

  Very shortly after Turing returned to Bletchley Park, the momentous breakthrough came. The veteran Frank Lucas recalled: “On a snowy January morning of 1940, in a small bleak wooden room with nothing but a table and three chairs, the first bundle of Enigma decodes appeared. The four of us who then constituted Hut 3 had no idea what they were about to disclose.”8

  In addition to their factual content, these decodes produced an important psychological boost. In the days of the Phoney War, tension was high. No one had yet managed to stop the German army. All knew that Nazi territorial ambitions were virtually limitless. Along with the desperate scramble to rearm and train her forces, Britain was in a furious struggle to gain an advantage in intelligence. That first break into the army code of the previously unbreakable Enigma machine was a source of some relief.

  Perhaps the weight of the unrelenting pressure was behind an explosive row between Dilly Knox and Alistair Denniston. For reasons of security, Denniston had been extremely reluctant to let Alan Turing travel to Paris with the Zygalski sheets; Knox, on the other hand, felt that aid and assistance to the Polish and French cryptographers was a promise that the Park was honor-bound to keep. The argument came to a head when Knox wrote Denniston this sulphurous letter, opening “My dear Alistair”: