Alastair Denniston

Commander Alexander Guthrie (Alastair) Denniston CMG CBE RNVR (1 December 1881, Greenock – 1 January 1961, Milford on Sea) 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.

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

World War I and interbellum
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.

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.

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

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

In October 1941, four senior codebreakers, Alan Turing, Gordon Welchman, Stuart Milner-Barry and Hugh Alexander had written 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. There was praise for the 'energy and foresight' of Commander Travis.

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

Personal and Post-war life
Denniston and his wife had two children: a son and daughter. The son, Robin had a good education at Westminster School and Christ Church, Oxford. After Alistair's demotion, Robin's school fees were paid by friends. Robin distinguished himself as a publisher. He researched and published a biography of his father. Sadly, the daughter had to leave her school.

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

Honours and awards

 * 7 January 1918 appointed an Officer of the Order of the British Empire (OBE) Commander Alexander Guthrie Denniston, R.N.V.R. Naval Intelligence Division, Admiralty.


 * 2 January 1933 appointed a Companion of the Order of the British Empire (CBE) Commander Alexander Guthrie Denniston, O.B.E., R.N.V.R. Head of a Department, Foreign Office.


 * 12 June 1941 appointed a Companion of the Order of St Michael and St George (CMG) Commander Alexander Guthrie Denniston, C.B.E., R.N.V.R. (Retd.), Head of a Department of the Foreign Office.