Key figures in UK Sigint
The great mathematician G. H. Hardy described C. H. O'D. Alexander as the only genuine mathematician he knew who did not become a professional mathematician. Hardy recognised that Alexander's failure to win a fellowship at the Cambridge Tripos exams was most likely due to his attention being absorbed by chess. Conversely, Alexander's fellow chess International Master Harry Golombek said of the two-time British Champion "the demands of his profession left him with comparatively little time for [chess] practice and study; otherwise he would certainly have been of true grandmaster class, and possibly even of world stature". Above both chess and mathematics, Alexander prioritised leading the British Government effort on cryptanalysis.
Alexander was an early recruit to Bletchley Park; he began in Hut 6 working on Army and Luftwaffe Enigma messages before moving in 1941 to Hut 8 to join Alan Turing's work on the Naval Enigma. Alexander had one of the most agile minds of the new breed of mathematical cryptanalysts; he proved the best at the pen and paper methods of 'banburismus' that reduced the computational work of Enigma attacks and his military aptitude test assessed him as suitable for development up to four star general. Although he has not achieved the renown of Good, Turing, Tutte, and Welchman, he was responsible for many breakthroughs. Perhaps the most significant was spearheading the UK-US joint work breaking the Japanese CORAL system used by Naval attaches. More importantly, as a former teacher and head of research at John Lewis, Alexander was much better suited to the organisational and administrative tasks of Hut 8 than the hyper-rational Turing. Alexander gradually assumed more and more of this work. The story goes that one day when Turing arrived late at the Park and the record book asked him to name the head of his section; Turing wrote "Mr Alexander" and with the logic of bureaucracy Alexander was treated as the head of Hut 8 from then onwards. Praise for Alexander's leadership is a theme common to all those who worked in Hut 8.
After the war, Alexander briefly returned to John Lewis before returning to the new GCHQ and continued to excel as both a cryptanalyst and leader. By 1949 he had been appointed head of the cryptanalysis division. It was a post that he held until his retirement, despite offers of promotion to more senior positions. He used the weight of his position to testify strongly as a character witness on behalf of Alan Turing during Turing's indecency trial. By 1971, already past the age of retirement by two years, Alexander decided to step down. Both GCHQ and their partners were keen to make continued use of his expertise and offered all manner of consultative work, which he declined. He died in 1974 and although his obituaries rightly spoke in glowing terms of his chess achievements, the impact of his more secret work still cannot be fully revealed.
Emily Anderson joined MI1b, the Interception and cryptanalysis section of the War Office, in 1918. She was the only woman Junior Assistant at the formation of GC&CS in 1919, by far the most capable of the JAs, and was Head of the Italian Diplomatic section by 1927. She was considered the leading book-builder in GC&CS and expected her own high standards in her colleagues and subordinates: Tiltman wrote that 'she seemed to bully any of my attached officers who worked under her'.
She accepted a posting to GHQ Middle East in July 1940 and was appointed OBE in July 1943 for her work there. She returned to the UK to work on diplomatic targets, and after the war stayed on in GCHQ. Her work in editing and publishing the letters of Mozart and Beethoven led the German government to award the Officer's Cross of the German Order of Merit.
Mavis Batey's story is well known, and when she died in 2013 the obituaries told her story about her time at Bletchley Park: working in The Cottage as one of Dilly Knox's "Girls"; not only breaking the message revealing that the Italian Navy was at "D-3" readiness for an action, but realising its significance and making sure that it was acted on; and playing a key role in breaking Abwehr Enigma.
Less interesting, perhaps, to the general reader, but of great long term significance to those who followed in her footsteps was her share of the writing up of how Abwehr Enigma was broken. Mavis, her husband, Keith, Margaret Rock and Peter Twinn compiled the official history of this work: GC&CS Secret Service Sigint Vol II: Cryptographic Systems and their Solution. Batey, Batey, Rock and Twinn as it is usually known (which, the GCHQ joke ran, sounded like a firm of solicitors in the Home Counties) describes in detail an important facet of the brilliant work carried out by cryptanalysts in Bletchley. Its sensitivity was such that GCHQ only released it in 2011. An original volume is now in The National Archives (reference HW 43/7) but GCHQ's Historian also presented a copy to Mavis at Bletchley Park which is held in the Bletchley Park Trust's own archive to celebrate their achievement.
Joan Clarke went to Cambridge to study Mathematics, and was awarded a double First in 1940. One of her supervisors was Gordon Welchman who persuaded her to come to Bletchley Park after completing her studies. On arrival she was not put into Hut 6 with Welchman, but instead was assigned to work with Turing in Hut 8. Turing was a friend of Joan's older brother Michael. She became adept at 'Banburismus', an application of Bayesian statistics which made large savings of processed time on the Bombes. She remained in Hut 8 for the rest of the war.
Joan became engaged to Turing in the spring of 1941: their families were informed, but it was kept secret from their colleagues. The engagement was broken off later that year because Turing was gay, but they remained friends for the rest of his life. Joan was one of the first people he wrote to after his arrest.
After the war, Joan became engaged to an Army integree, Lt Col Jock Murray, who she married in 1952. She rejoined GCHQ in 1962, working in cryptanalysis for the rest of her career. After retirement she was asked to work with Sir Harry Hinsley, who was writing the official history British Intelligence in the Second World War, correcting the first inaccurate account of the respective contributions of the British, the French and the Poles to the solution of Enigma.
A lecturer at the Naval College at Osborne in 1914, A G Denniston was a member of Room 40 from its beginning during the First World War. He became the first head of the Government Code & Cypher School (GC&CS) in 1919, and led the organisation during the inter-war years.
Although GC&CS focused mainly on reporting diplomatic traffic, it was with Denniston’s agreement that the first commercial Enigma machine was bought in 1926, and it was he, when faced with the inability of his cryptanalysts to break into German military Enigma, who agreed to open the talks with the French, and subsequently the Poles who were ahead of their allies and were able to impart the information which would be the foundation of Bletchley Park's success.
It was his foresight which led to the identification of new talent - most famously Alan Turing - for the organisation in 1938, and his inspiration which moulded a diverse group of people into the successful Bletchley Park team: he was ahead of his time in understanding the value which could be brought to Sigint by people with neural difference if they were allowed to be themselves.
He oversaw the move from London to Bletchley Park in 1939 and led the establishment of closer liaison with the USA, hosting a US team in February 1941 and making a dangerous return trip later that year.
Bletchley Park was reorganised in January 1942. Denniston was unceremoniously moved sideways and sent to run Diplomatic and Commercial Signals Intelligence in Berkeley Street in London. He retired in 1945 and died in 1961.
James Ellis, a mathematician and computer scientist, joined GCHQ in 1952. He worked on a number of important cryptographic developments, but his identification of the concept of Public Key Cryptography (PKC) was the most significant and far-reaching.
This discovery remained classified for a long time and was, at first, only made available for official governmental communications. However, PKC was later thought of independently and developed commercially, and is now the basis for all secure transactions on the Internet.
Flowers was involved in the construction of the Heath Robinson machine, but used the insights he had about the design of electronic telephone exchanges to think of a complex valve-based machine: this was COLOSSUS, the forerunner of the modern computer, and Flowers led the team which built it. Even before the first COLOSSUS had been built, he was adding improvements to COLOSSUS 2. Eventually, ten COLOSSUS machines were built, and their output provided vital intelligence for the Military, particularly before D-Day. After the war eight of the machines were dismantled so that the parts could be recycled, but GCHQ kept two for its own use.
Tommy Flowers returned to the Post Office and resumed his work on electronic exchanges. Because of the continuing sensitivity about cryptanalytic success during the war, and particularly the use of computers in cryptanalysis, he had retired before the story of his crucial role in the development of modern computing could be told.
Nigel de Grey
In 1917, Nigel de Grey, also a Room 40 cryptanalyst, played the key role in decrypting the Zimmermann Telegram and recognising it as potentially the key to bringing the USA into the war on the Allied side.
He left Room 40 at the end of the war, but joined Bletchley Park in 1939, becoming the Assistant Director mainly responsible for intelligence production, and remained at GCHQ after the war.
Alfred Dillwyn 'Dilly' Knox
A Greek scholar, Dilly Knox was another member of Room 40. His main expertise was in "Research"; the diagnosis of crypt systems and the development of techniques to break them. He came close to understanding military Enigma, though he missed one of its crucial variables. He was generous in his praise of the success his Polish counterparts had.
Rolf Noskwith was a rare example of someone who joined Bletchley Park having a good idea of what work was being done there. As a maths undergraduate at Cambridge who spoke German and enjoyed solving crosswords, he was recommended by the University Recruitment Board to join the Officer Training Corps in Artillery Survey Work but for the Army to use his knowledge of languages and his interest in decoding. In the event he was deemed medically unfit to serve in the Armed Forces and so continued his studies.
In early 1940 he was interviewed by Gordon Welchman and offered a job at Bletchley Park but the discovery that he was not British-born meant that his appointment was vetoed. In 1941, his final year at university, he was again interviewed, this time by CP Snow (at the time a Civil Service Commissioner) and Hugh Alexander. The veto was lifted, he was once again offered a job, and he joined Bletchley Park on 20 June 1941 as soon as he had finished his Finals. He was sent to Hut 8 to work, under Alexander, on German Naval Enigma. He discovered a knack for cribbing and remained a Hut 8 cribster for the rest of the war. He had a varied social life at Bletchley Park, enjoying bridge and chess and attending concerts. He was also a member of the Bletchley Park Home Guard platoon. After VJ Day he stayed on at GCHQ, moving to Eastcote and working under John Tiltman for a while before leaving to join the family business.
For more about the contribution made by Rolf Noskwith and the other Jewish codebreakers at Bletchley Park see the article written by Robert Hannigan, Director GCHQ, published in the Jewish Chronicle.
Brigadier John Tiltman MC
John Tiltman was first attached to GC&CS in 1920. He founded the Military Section and remained its Head throughout the Second World War. In 1938 Tiltman had a desk made for him in Hong Kong which was subsequently in the office of successive Chief Cryptanalysts at GCHQ. It is now on display at GCHQ in Cheltenham.
Between the wars, he is best remembered for MASK, the work he led against the Comintern. He was responsible for the first British success against the main Japanese naval code, JN25, shortly after it was introduced in June 1939. And in 1941 he deciphered the message which led eventually to the solution of the German High Command's teleprinter system 'Tunny'.
He played a crucial part in developing relationships with US Sigint authorities and after eventually retiring from GCHQ, he went to work at NSA where he remained until he was 80.
Posthumously, the most famous alumnus of Bletchley Park, Alan Turing was recruited in 1938 and, after taking part in some specially devised courses, joined Bletchley Park in September 1939.
He met Polish counterparts in Paris in January 1940, a meeting at which they gave him the insights he needed to build on their foundations by designing the Bombe. This was the first special-purpose cryptanalytic machine, and made major contributions to the exploitation of German Naval Enigma, before moving on to work on secure speech systems.
After the war, working at Manchester University, he and Max Newman, another BP mathematician, led a team that produced Britain's first general-purpose stored programme computer (the Ferranti Mk 1).
Gordon Welchman joined Bletchley Park in September 1939. He had a gift for planning and organisation and was appointed Head of Hut 6: he conceived the "diagonal board": a dramatic improvement to Turing's Bombe. Appointed Head of Machine Coordination and Development Section in September 1943, he was responsible for the security of machine cyphers, the development of cypher machines and machines for communications and interception.
Welchman wrote many constructive policy papers for Travis on Bombes and machine processing. He reached Directorate level in March 1944 when appointed Assistant Director of Machines and Mechanical Devices.
His brilliant career at Bletchley Park was overshadowed by controversy when he published details of his wartime work against the wishes of UK and US authorities in the early 1980s.