Alastair Denniston

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Alastair Denniston
Born Alexander Guthrie Denniston
(1881-12-01)1 December 1881
Greenock, Scotland
Died 1 January 1961(1961-01-01) (aged 79)
Lymington, Hampshire
Fields Cryptologist
Alma mater University of Bonn
University of Paris

Commander Alexander (Alastair) Guthrie Denniston CMG CBE RNVR (1 December 1881 - 1 January 1961) was a British codebreaker in Room 40 and first head of the Government Code and Cypher School (GC&CS) and field hockey player. Denniston was appointed operational head of GC&CS in 1919 and remained so until February 1942.[1]

Early life[edit]

Olympic medal record
Men's field hockey
Bronze 1908 London Team

Denniston was born in Greenock, the son of a medical practitioner.[1] He studied at the University of Bonn and the University of Paris.[1] Denniston was a member of the Scottish Olympic Hockey team in 1908 and won a bronze medal.

World War I and interbellum[edit]

In 1914 he helped form Room 40 in the Admiralty, an organisation responsible for intercepting and decrypting enemy messages. In 1917 he married a fellow Room 40 worker, Dorothy Mary Gilliat.[1]

After World War I, Room 40 was merged with its counterpart in the Army, MI1b, to become the Government Code and Cypher School in 1919. Denniston was chosen to run the new organisation.

On 26 July 1939, just five weeks before the outbreak of World War II, Denniston was one of three Britons (along with Dilly Knox and Humphrey Sandwith) who participated in the trilateral Polish-French-British conference held in the Kabaty Woods south of Warsaw, at which the Polish Cipher Bureau initiated the French and British into the decryption of German military Enigma ciphers.[2]

World War II[edit]

With the outbreak of World War II in 1939, GC&CS greatly expanded and relocated to Bletchley Park.

In October 1941, four senior codebreakers, Alan Turing, Gordon Welchman, Stuart Milner-Barry and Hugh Alexander wrote to Churchill, over the head of Denniston, to alert Churchill to the fact that a shortage of staff at Bletchley Park was preventing them from deciphering many messages. An addition of man or womanpower, small by military standards, could make a big difference to the effectiveness of the fighting effort. The slow response to previous requests had convinced them that the strategic value of their work was not understood in the right quarters. In the letter, there was praise for the 'energy and foresight' of Commander Edward Travis.[3]

Churchill reacted to the letter immediately, ordering "Action this day". Resources were transferred as fast as possible.

In February 1942, GC&CS was reorganised. Denniston was effectively demoted, placed in charge of a civil and diplomatic division in London. Travis succeeded Denniston at Bletchley Park, overseeing the work on military codes and ciphers.

When Travis took over, he "presided over an administrative revolution which at last brought the management of Intelligence into line with its mode of production".[3]

Personal and Post-war life[edit]

Denniston and his wife had two children: a son and daughter. The son, Robin, was educated at Westminster School and Christ Church, Oxford. After Alistair's demotion, Robin's school fees were paid by benefactors. The Dennistons' daughter had to leave her school.[4]

Denniston retired in 1945, and later taught French and Latin in Leatherhead.[1]

Robin distinguished himself as a publisher. In 2007, he published Thirty Secret Years, a biography of his father that consolidated his reputation in GCHQ history.[4]

Honours and awards[edit]


  1. ^ a b c d e f F. H. Hinsley, revised by Ralph Erskine, "Denniston, Alexander Guthrie [Alastair] (1881-1961), cryptanalyst and intelligence officer", Oxford Dictionary of National Biography, 2004
  2. ^ Ralph Erskine, "The Poles Reveal their Secrets: Alastair Denniston's Account of the July 1939 Meeting at Pyry", pp. 294-305, Cryptologia 30(4), 2006
  3. ^ a b Hodges, Andrew (1983), Alan Turing: the Enigma, pp 219-223
  4. ^ a b The Daily Telegraph, 27 May 2012 Obituary: Robin Denniston
  5. ^ The London Gazette: (Supplement) no. 30460. p. 377. 7 January 1918. Retrieved 2008-11-20.
  6. ^ The London Gazette: (Supplement) no. 33898. p. 9. 2 January 1933. Retrieved 2008-11-20.
  7. ^ The London Gazette: (Supplement) no. 35814. p. 3284. 12 June 1941. Retrieved 2008-11-20.


External links[edit]

Government offices
New title Deputy Director of GC&CS
later Deputy Director (Diplomatic and Commercial)
Succeeded by
Sir Edward Travis