The Bletchley Park Codebreakers (2 page)

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BLETCHLEY PARK IN PRE-WAR PERSPECTIVE

CHRISTOPHER ANDREW

Bletchley Park may well have been the best-kept secret in modern British history. The 10,000 men and women who worked there were, in Churchill’s famous phrase, ‘the geese who laid the golden eggs and never cackled’. Ultra, the intelligence produced at Bletchley Park from the breaking of high-grade enemy ciphers and the analysis of intercepted signals, was the best intelligence in the history of warfare. But if the secret had leaked out, Ultra would have been worthless. At the end of the Second World War most of those who had been ‘indoctrinated’ into Ultra believed that it would never be revealed. Not until the secret was declassified in the mid-1970s did the geese begin to cackle. A student at my Cambridge college told me how, together with his parents and his sister, he had watched the first BBC documentary on Bletchley Park which showed wartime Wrens (members of the Women’s Royal Naval Service) operating the ‘bombes’ used to break the German ‘Enigma’ machine ciphers. At the end of the programme, his mother turned to the rest of the family and told them, ‘That’s where I worked. That’s what I did.’ Until that moment neither her husband nor her children had had any idea that she had been a wartime codebreaker. The most extraordinary thing about this extraordinary
episode is that, so far as the codebreakers were concerned, it was not unusual. Shortly before the publication in 1979 of the first volume of Sir Harry Hinsley’s official history,
British Intelligence in the Second World War
, he addressed a large reunion of Bletchley Park veterans and their spouses. After the address, the husbands of a number of former Wrens told Hinsley, ‘She never breathed a word to me.’

For the mostly youthful wartime recruits to Bletchley Park indoctrination into Ultra was an unforgettable emotional experience which had few, if any, previous parallels in the entire course of British history. Until their recruitment, hardly any of these people were even aware that Britain had a signals intelligence (Sigint) agency. Yet they suddenly found themselves, during Britain’s ‘finest hour’, in possession of a secret whose revelation might do irreparable damage to the war effort. No wonder that some, perhaps many, suffered from nightmares in which they unwittingly gave the secret away. The extraordinary success with which the Ultra secret was kept for so long reflected in part a national culture which embodied far greater respect for official secrecy and deference to authority than is imaginable today. Despite joining the anti-war movement only six years before he arrived at Bletchley Park, Alan Turing, one of the greatest of the wartime codebreakers, seems to have been untroubled even by peacetime doubts about the essential importance of official secrecy. During the Abdication Crisis of 1936, though at first ‘wholly in favour of the King [Edward VIII] marrying Mrs Simpson’, Turing had second thoughts after ‘It appeared that the King was extremely lax about state documents, leaving them about and letting Mrs Simpson and friends see them.’

In itself, however, a traditional national culture of official secrecy is an inadequate explanation for the extraordinary success with which the Ultra secret was maintained for so long. Some of the secrets of British codebreaking during the First World War had begun to leak out almost as soon as the war was over. In his great history of the war,
The World Crisis
, Winston Churchill, later among the staunchest defenders of the Ultra secret, vividly recalled his excitement while First Lord of the Admiralty for the first nine months of the war at receiving decrypted German naval radio messages which, on occasion, were delivered to him even in his bath, where he eagerly ‘grasped [them] with dripping hand’. During the 1920s, some of the early successes of Britain’s newly established peacetime Sigint agency, the Government
Code and Cypher School (GC&CS), against the Soviet Union were revealed in both the press and government statements. Churchill’s own attitude to Sigint security at the time now seems remarkably naive. He wrote in the summer of 1920 that the ‘perfidy and treachery’ contained in Soviet diplomatic decrypts was such that their contents should be made public:

In September 1920, the
Daily Mail
and the
Morning Post
published details from the decrypts of secret Soviet subsidies to the socialist
Daily Herald
. In May 1923, the Cabinet authorized the Foreign Secretary, Lord Curzon, to quote Soviet diplomatic decrypts in a protest note to Moscow, chiefly concerned with Soviet subversion in India and India’s neighbours. The protest note, swiftly christened the ‘Curzon ultimatum’, was unprecedented in the history of British diplomacy. Not content with quoting from Soviet decrypts, Curzon repeatedly taunted Moscow with the fact that its secret telegrams had been successfully intercepted and decrypted by the British:

The new ciphers, introduced by Moscow in an attempt to make its diplomatic traffic more secure after the Curzon ultimatum and other British breaches of Sigint security in the early 1920s, were successfully broken by British cryptanalysts after varying intervals. In 1927, however, Britain’s ability to decrypt Soviet diplomatic traffic was fatally undermined by another extraordinary governmental indiscretion. The Baldwin Cabinet, of which Churchill was a member,
decided to publish a selection of Soviet intercepts in order to justify its decision to break off diplomatic relations with Moscow. Austen Chamberlain, the Foreign Secretary, gave his message to the Soviet chargé d’affaires breaking off relations a remarkably personal point by quoting a decrypted telegram from the chargé to Moscow ‘in which you request material to enable you to support a political campaign against His Majesty’s Government’. A. G. Denniston, the operational head of GC&CS, wrote bitterly that Baldwin’s government had deemed it ‘necessary to compromise our work beyond question’. Henceforth Moscow adopted the theoretically unbreakable ‘one-time pad’ for its diplomatic traffic. For the next twenty years British cryptanalysts were able to decrypt almost no high-grade Soviet diplomatic traffic (though they continued to have some success with communications of the Communist International).

The lessons learned from the Sigint catastrophe of 1927, as a result of which Britain lost its most valuable interwar intelligence source, were crucial to the later protection of the Ultra secret. No politician took those lessons more to heart than Winston Churchill. After he became prime minister, at his personal insistence the circle of those who shared the secret of the cryptanalysts’ ‘golden eggs’ was limited to only half a dozen of his thirty-six ministers. The Special Liaison Units set up to pass Ultra to commanders in the field were the most sophisticated system yet devised to protect the wartime secrecy of military intelligence. The profound change in Churchill’s attitude to Sigint security is epitomized by the contrast between his published accounts of the two world wars. In his memoirs of the First World War, Churchill had written lyrically of the importance of Sigint; in his memoirs of the Second World War there is no mention of Ultra.

As well as being crucially dependent on the lessons learned in 1927, Ultra also owed much to precedents set in the First World War. The creation of GC&CS in 1919 was itself a consequence of the fact that Sigint had proved its value during the war. Without the expertise painstakingly built up by Denniston on minimal resources between the wars, Bletchley Park’s wartime triumphs would have been impossible – despite the invaluable assistance provided by the Poles and French on the eve of war. The breaking of Enigma in its wartime variations required a major new intelligence recruitment. In 1937, the Chief of the Secret Service, Admiral Sir Hugh ‘Quex’ Sinclair, told Denniston that he was now ‘convinced of the inevitability of war’ and gave
‘instructions for the earmarking of the right type of recruit immediately on the outbreak of war’ – chief among them what were quaintly called ‘men of the professor type’. The most active recruiters of ‘professor types’ were two Fellows of King’s College, Cambridge, who had served in Room 40, the main First World War Sigint agency: Frank Adcock (later knighted), Professor of Ancient History, and the historian Frank Birch, who left Cambridge for the stage in the 1930s. Both inevitably looked for recruits in the places they knew best: Cambridge colleges in general and King’s in particular. A total of twelve King’s dons served at Bletchley during the Second World War. By great good fortune the King’s Fellowship included Alan Turing, still only twenty-seven at the outbreak of war, one of the very few academics anywhere in the world to have carried out research into both computing and cryptography. Turing’s pioneering paper, ‘Computable Numbers’, now recognized as one of the key texts in the early history of modern computer science, was published early in 1937, though it attracted little interest at the time. Three months before its publication Turing, then at Princeton, wrote to tell his mother that he had also made a major breakthrough in the construction of codes. In view of his later exploits at Bletchley Park, Turing’s letter now seems wonderfully ironic:

Turing went on to become the chief inventor of the ‘bombes’ used to break Enigma.

The search for ‘professor types’, of whom Turing was probably the most remarkable, even in a highly distinguished field, followed two important precedents established during the selection of British codebreakers in the First World War: the recruitment of unusually youthful talent and of original minds who would have been regarded as too eccentric for employment by most official bureaucracies. (The two categories, of course, overlapped.) Two of Britain’s leading codebreakers in the two world wars, Dillwyn ‘Dilly’ Knox and Alan Turing, both Fellows of King’s, were also among the most eccentric. Knox, a classicist, did some of his best work for Room 40 lying in a bath in Room 53 at the Admiralty Old Building on Whitehall, claiming that codes were most easily cracked in an atmosphere of soap
and steam. Frank Birch wrote affectionately of Knox in his classified satirical history of Room 40,
Alice in ID25:

Knox’s bathtime cryptanalysis continued during his time at Bletchley Park, once causing fellow lodgers at his billet, when he failed to respond to shouted appeals through the bathroom door, to break down the door for fear that he might have passed out and drowned in the bath.

Turing’s eccentricities make such engaging anecdotes that they are sometimes exaggerated, but there can be no doubt about their reality. His ability from a very early age to disappear into a world of his own is wonderfully captured by a drawing of him at prep school by Turing’s mother, which she presented to the school matron. The drawing, entitled ‘Hockey or Watching the Daisies Grow’, shows the ten-year-old Turing, oblivious of the vigorous game of hockey taking place around him, bending over in the middle of the pitch to inspect a clump of daisies. At Bletchley Park he chained his coffee mug to a radiator to prevent theft, sometimes cycled to work wearing a gas mask to guard against pollen, and converted his life savings into silver ingots which he buried in two locations in nearby woods. Sadly, he failed to find the ingots when the war was over. The informality and absence of rigid hierarchy at Bletchley Park enabled it to exploit the talents of unconventional and eccentric personalities who would have found it difficult to conform to military discipline or civil service routine.

Most of the dons and other professionals recruited by Room 40 had been young. The ‘professor types’ selected by Bletchley Park were, on average, younger still. In the summer of 1939, Alastair Denniston wrote to the heads of about ten Cambridge and Oxford colleges, asking for the names of able undergraduates who could be interviewed for unspecified secret war work. Among the twenty or so recruited during the first round of interviews (repeated on a number of later occasions during the war) was the twenty-year-old Harry Hinsley, who was about to begin his third year as an undergraduate historian at St John’s
College, Cambridge. After Pearl Harbor, when Bletchley Park needed more cryptanalysts and linguists to take newly devised crash courses in the Japanese language, the recruitment included sixth-formers as well as undergraduates – among them Alan Stripp, recruited after winning a classics scholarship to Trinity College, Cambridge, who later
co-edited
with Hinsley a volume of memoirs on Bletchley Park. During a visit to Bletchley, Churchill is said to have remarked ironically to Denniston, as he surveyed the unusually youthful staff, ‘I told you to leave no stone unturned to get staff, but I had no idea you had taken me literally.’