Knox had a very powerful intellect but tended to be incomprehensible and intolerant of people who could not understand him. This was partly due to his background, which was classical rather than mathematical. He worked at one time on Hungarian and did not trouble to learn the language, treating the whole thing as an abstract problem. I remember him coming to me with a piece of paper covered with cipher groups with marks in coloured chalks over them. It was, he said, an account of an interview with an Italian diplomat. Did I have anything in Italian diplomatic ciphers on the same subject? ‘This group taken with that one means that either Mussolini or Stalin did, or did not, say that the man named in this group, who may be Sir Samuel Hoare, is going to speak at the League of Nations,’ he said. I could only say that I did not have anything to fit. ‘Well, the Hungarian is probably lying anyway,’ Dilly said, shuffling out of the room.
Nevertheless, a code was a code and was there to be broken, intelligence or no intelligence; as Alastair Denniston recorded in his own memoir of the period, ‘Hungarian was successfully broken by Knox, but it is doubtful if the results obtained at that time justified the enormous effort on his part.’
Although the Russian diplomatic material had dried up, an entirely new type of Russian traffic was emerging which would occupy Dilly more usefully than diplomatic Hungarian had done. Our wireless stations began to pick up a mass of secret radio transmissions all in cipher, except for the operators’ chat, which was of the international amateur type. ‘The analysis of this traffic was studied closely and from it emerged a worldwide network of clandestine stations controlled by a station near Moscow,’ Denniston recalled. ‘It turned out to be the Comintern network.’ Its aim was the creation of a worldwide Soviet socialist republic. In 1929, John Tiltman, a former army officer, was recalled to England from India, where he had been reading Russian diplomatic traffic with Afghanistan and Turkestan, to head the new military section of GC&CS. He was a Russian expert and took over the new traffic, which he and Dilly soon broke into. Hundreds of the resulting decrypts, codenamed Mask, covering the period from 1930 to 1937, were released in 1997.
The Mask material produced by Dilly and Tiltman was of critical importance to Britain’s intelligence war against the Soviet Union in this first Cold War. The attack by Dilly and Tiltman on the Mask ciphers met with ‘complete success’ and the material passed to SIS allowed Britain’s spies to recruit a number of agents inside the Comintern in France, Holland, and Scandinavia and was a key factor in a number of major successes, most notably the dismantling of the Soviet networks in the Far East. It also provided further evidence of the links between Moscow and the Communist Party of Great Britain and led to the arrest of a number of Soviet agents in Britain.
Dilly and Tiltman would continue to collaborate into and during the Second World War. The military man with his highly efficient methods for getting into ciphers was never likely to be close to Dilly given the latter’s penchant for Carrollian chopped logic, but despite their differences they worked well together, each respecting the other’s strengths and spheres of responsibility, which is the way Dilly liked to operate. Tiltman, as a military man, remained in charge of the military section of GC&CS at Broadway and also at Bletchley Park, whereas Dilly, although turning his hand to any codebreaking problem, particularly relished any work associated with the naval section, which Sinclair had asked ‘Nobby’ Clarke to set up as early as 1924. Dilly always had a very easy relationship with ‘Nobby’.
Dilly remained in touch with his brothers whenever he could and mostly with Ronnie, who was sometimes at a loose end when he was teaching at St Edmund’s College in Hertfordshire, before he was given the Oxford chaplaincy in 1926. Whereas none of Dilly’s literary efforts or puzzles were ever in print, Ronnie decided to publish his and earn an honest penny. Eddie had for some time been sending contributions to Punch and would become the magazine’s editor in 1932. The Knox brothers had always enjoyed creating acrostics – poems where the first letters of each line spell out a word – and in 1924 Ronnie published The Book of Acrostics collected from periodicals. Needless to say one of their favourite acrostics was Lewis Carroll’s Golden Afternoon, which begins:
A boat, beneath a summer sky
Lingering onwards dreamily
In an evening of July,
Children three that nestle near,
Eager eye and willing ear.
Dilly had another idea for a verse form which he called a ‘pentelope’, where each line must end with a word of the same form, but with a different vowel which must appear in the proper order, either in spelling or pronunciation. Perhaps there was a hint of a variation of a column of pronounceable code-groups in the pentelopes. These were never publicised but were piled into a tin. Dilly felt the day that the poet A. E. Housman died called for a pentelope:
Sad though the news, how sad [A]
Of thee, the poet, dead! [E]
But still, the poems abide [I]
There death, the unsparing god [O]
Himself dare not intrude [U]
Dilly’s younger son, Oliver, particularly enjoyed his father’s acrostics and pentelopes and memorable way of putting things. He would one day become an advertising executive and later worked for Margaret Thatcher’s Centre for Policy Studies. His Knoxian advice to them was that ‘government policies ought to be presented in an entertaining fashion. Limericks are remembered long after White Papers.’ Oliver Knox worked on Japanese ciphers at Bletchley Park after his father’s death and found his reputation thriving. This was the first time he understood what Dilly’s wartime work had been. He told the story of early frustrations in trying to find out what his father did:
To his work he referred not at all, any enquiries in that respect being met with the dismaying device of total silence. Once at WH Smith’s in High Wycombe, I bought a cheap primer about elementary codes. Perhaps by leaving it about casually on the dining room table, I might lure one of my parents to reveal just a glimpse or two about a world which seemed nearly as exciting as spying. I could promise my undying silence, of course. Ridiculous useless bait! The book was not even cleared from the table; there was silence over the sardines on toast.
Although pentelopes never hit the headlines, there was one Knox pursuit in the twenties which did, and that was a new genre of whodunit detective stories with strict logical rules. In 1925, Ronnie published the first of six such novels, The Viaduct Murder, in which a clergyman, a don, someone from intelligence and a holidaymaker were playing golf together and hit a ball under a viaduct only to find a dead body; they try to solve the mystery in their own special ways with the clues given. Evelyn Waugh, Ronald Knox’s literary executor and biographer, saw these detective novels as intellectual exercises, a game between the writer and the reader in which a problem was precisely stated and elaborately disguised. ‘As his brother Dillwyn had systematised and regulated the haphazard games of the Birmingham schoolroom,’ Waugh said, ‘so Ronald observed and sought to impose a code of rules, which he later set out in his introduction to The Best Detective Stories of the Year in 1928. The criminal must be mentioned in the first five chapters and the reader must not be allowed to know his inner thoughts; no unknown poisons nor mysterious Chinamen; the detective must declare all the clues, as must the “Watson” or uncomprehending friend, were but a few.’ These rules were adopted in 1929 as the Solemn Oath of the Writers’ Detection Club, which included G. K. Chesterton, Agatha Christie and Dorothy Sayers. Dilly got to know and like Christie, who broke most of the rules and somehow managed to apologise for it.
The most entertaining of their father’s friends, whom Christopher and Oliver were always glad to see at Courns Wood, was Frank Birch, who having resigned as a history don at King’s had become a theatre producer and actor. A highlight in the children’s life was when Dilly treated as many of the family as could be mustered to seats at the Lyric, Hammersmith to see Birch’s splendid performance as the Widow Twankey in Aladdin. When the children saw another weekend visitor,
the formidable Professor Edgar Lobel from Oxford, approaching they quickly disappeared as they knew he had come over to tell their father about the latest papyrus discoveries at Oxyrhynchus and attempt to reconstruct the ancient world with him. ‘If Edgar Lobel was the most imposing of my father’s friends, Frank Birch was the jolliest, most amusing and mondain,’ recalled Oliver. ‘When he came down to Courns Wood, I was slightly ashamed of the cold unworldliness of our home, and vaguely conscious that the half-bottle of Châteauneuf du Pape customarily provided for visitors was not enough.’
Dilly could not resist another return to Herodas and Cercidas for the 1929 Loeb Classical Edition, part of a series founded in 1911 to make classical authors accessible with Greek on one side of the page and English on the other. If the Herodas Mimiambi poems were good enough, Dilly translated them skilfully, reproducing the metre, as well as the sense of the Greek verse.
But now that there gleam on my head
White hairs but a few at the edge
Still does my summer
Seek for the thing that is fair.
However, there was now something at Courns Wood that did indeed make his summers fair. He had developed a passion for tree-planting and had even bought more adjacent land. He spent weekends happily in the woods with his two small sons making log cabins for them and a scaffold on wheels so that they could be at his height to watch him sawing the tops of trees. He liked to talk to the famous Chiltern bodgers in the beech woods, making chair legs for the High Wycombe furniture industry, and he learned a lot from them. In 1931, he had an accident on his motor cycle and his leg was badly broken, after which he always walked with a limp. He had to buy an Austin Seven to cover the five miles to get him to the station and the family wondered how long it would be before he had an accident in that, as he used to take his hands off the steering wheel when going downhill and recite his favourite poem Lycidas with its inspiring last lines ‘tomorrow to fresh woods and pastures new’.
The artist Gilbert Spencer, whose portrait of Dilly appears on the cover, lived at the bottom of the road leading up to Courns Wood and Dilly always gave him a lift to the station in the morning. Dilly ‘used to amuse himself by seeing how far he could go downhill with the engine off,’ Spencer said. ‘He also told me that our terminus (Marylebone) was so out of the way that he was pretty nearly the only passenger, which explained why he was so politely received by the station-master. But we thought it was his highly important position at the Foreign Office.’
Change was clearly being considered as, in 1934, Dilly wrote to John Maynard Keynes, as bursar of King’s, with a proposal that the college should take responsibility for his now flourishing woodlands; that this was a part of a contemplated move back to Cambridge is confirmed by Oliver Knox’s reminiscences of a conversation he overheard, when he was in the log cabin, about this time. What he heard, he said, was disturbing.
My father was talking of the frustrations of life in Whitehall and his yearning to resume his work on the obscurer corners of early Greek literature. My mother was reminding him, quietly but firmly, of his duty to educate his sons and of the national importance of his work, for good measure adding that she herself could not bear to return to the chill wastes of fenland and the inhospitable society of dons. I didn’t dare to shuffle or in any way betray my presence but peeped through the cracks in the planks of the wall. My father was in his shirt sleeves, holding his saw. His pipe lay neglected on the makeshift window sill. For once he wasn’t wearing his horn-rimmed spectacles, so that his eyes looked unfamiliarly naked. This was one of the very few times indeed that I ever saw him looking as though he was not in control of his destiny.
The ‘obscurer corners of early Greek literature’ which Dilly wanted to resume concerned his work on the metre of the Greek plays and poems. He had already published an article in 1925 and had been in contact with the German classical scholar Ulrich von Wilamowitz-Moellendorff over a highly technical point on the metre within classical Greek poetry and drama, which Dilly developed in another Philologus article in 1932 entitled ‘The Early Iambers’ and was anxious to pursue. Although Olive managed to persuade him that his codebreaking work was more important, he would earn his place as a scholar of classical Greek through his recent discovery of a key law governing the metre of Greek lyrical drama and poetry. This was Dilly’s Greek swansong. It was fortunate that Olive prevailed as it would not be long before GC&CS presented him with a problem even more challenging than any he had ever encountered either in Room 40 or in the minds of Ionian dramatists and poets.
FIVE
Enigma
Cryptography, the art of secret communications, would be transformed by the advent of the cipher machine, particularly the Enigma, based by Arthur Scherbius on a secret writing machine invented by the Dutchman Hugo Alexander Koch. In 1923, Scherbius exhibited his machine with its striking art deco logo at the International Postal Union Congress and advertised it as a means of safeguarding the secrecy of cables and telegrams. What began life as a commercial enterprise was to end up as being a major influence on the outcome of battles. The businessmen of the world were slow in responding, however, but this was the year that British politicians had revealed how much wireless interception and Room 40’s codebreaking had contributed to the allied victory in the First World War. Germany had found means of defying the Versailles treaty, which only allowed the defeated enemy to take measures for security and counter-espionage, by calling its growing army the Reichswehr and its secret service the Abwehr, both implying defence; it now needed a means of hiding its secret communications. Scherbius seemed to be the answer as his pamphlet claimed that there were so many millions of ways of setting the machine that it would be impossible to break the messages without knowing the key settings. Germany seized the opportunity to acquire commercial machines and adapt them for military purposes.
GC&CS appointed Edward Travis, Alastair Denniston’s deputy, to take charge of all security aspects of British government communications and it therefore fell to him to investigate the commercial machine when the British patent was applied for in 1927. After an Enigma machine had been acquired for GC&CS, Travis asked Hugh Foss, who had joined GC&CS in 1924, to see if Scherbius’s claims that it was unbreakable were true. The elaborate sales pamphlet, produced in English under the title of The Glow-Lamp Ciphering and Deciphering Machine ‘Enigma’ showed that it looked like a typewriter in a wooden box with a standard keyboard (the continental QWERTZU instead of the British QWERTY) and above that a lampboard with a series of small light bulbs in the same order. The operator typed out the plain text message and the act of depressing the key sent an electrical impulse through the machine and the enciphered letter would show up on the lampboard, making commercial secrets safe for ever. Scherbius added in a non-committal way that ‘decisive battles have been lost, by land and by water, in the air and in debating with each other, because the adversary had a better method of keeping his correspondence secret’.
The British patent specification no. 267,472, accepted on 11 August 1927, set out exactly how the electrical ciphering machine worked. Stress was laid on the importance of being able to change the order of the three wheels, that it was possible to acquire extra, differently wired, wheels, and that ‘in the case of war’ there was the further advantage ‘that if surprised by the enemy it was only necessary to remove the wheels to render the machine useless’. The hint in the 1923 pamphlet had now turned into a bold statement about the importance of Enigma’s use in war. Accompanying photographs showed how to set the machine, the interchangeable order of the wheels, the clip or Ringstellung which set the moveable rings on the wheels and the Grundstellung, the basic starting position in which the letters on the wheels were to appear in the windows before enciphering the message key. The operator positioned the three wheels in a pre-determined order. The Germans chose to set the rings to the agreed Grundstellung and then selected three letters at random as the message setting. These were encrypted twice to produce a six-let
ter message indicator. The operator then set the wheels to the message setting and enciphered the message, pressing the key for every letter of plain text and reading off the enciphered letter on the lampboard. He sent the enciphered indicators in the preamble to his message. Foss painstakingly got down to the problem he had been set and was able to produce his report in 1928.
Foss called the machine the Reciprocal Enigma, as a previous large typewriter enciphering machine described in a patent of 1924 had only been a one-way machine with no reflector (Umkehrwalze) and consequently was non-reciprocal. The electric signal set off by depressing the key travelled through wiring of the wheels to the reflector, which sent the signal back through the wheels a second time and the enciphered letter lit up on the lampboard. The action of depressing the key also moved the first, or right-hand, wheel one notch forward. Periodically, the movement of this first wheel led the other wheels to move forward. This was known as a ‘turnover’. Foss considered that in spite of the high degree of security of the Scherbius Reciprocal Enigma, it could be broken, given certain conditions, if the codebreaker had obtained a piece of plain text or guessed it as a crib. If the wiring of the wheels was known, just fifteen letters were all that was needed to find the machine setting, but if the wheel wiring was unknown, at least 180 letters would be needed. It is uncertain whether, at this early stage, Dilly discussed the problem with Foss, who maintained that he was not making any attempt to provide a methodology for breaking an Enigma machine himself; that would be left to Dilly Knox to discover, but how much later is not clear. An unconfirmed statement quoted in Foss’s ‘Reminiscences on Enigma’, written in 1949, says that Dilly Knox purchased an Enigma machine in Vienna in 1925, which seems odd. With two young toddlers, he and Olive are unlikely to have been visiting Austria on holiday, although perhaps there was an exhibition of the machine which led to him going on his own to gather intelligence on how it worked. However, there is no doubt that there was one in GC&CS available after Foss completed his work in 1929; that being so, there is no question that Dilly would not have wanted to investigate it, whether or not, with all his other pressing Russian cipher commitments, he was officially asked to do so.
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