Joan Clarke

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Not to be confused with Joan Clark.
Joan Clarke
Born Joan Elisabeth Lowther Clarke
(1917-05-05)5 May 1917
Died 4 September 1996(1996-09-04) (aged 79)
Nationality English
Alma mater Newnham College, Cambridge
Occupation Cryptanalyst
Known for Codebreaking at Bletchley Park
Awards MBE

Joan Clarke MBE (1917 – 1996) was an English cryptanalyst who worked as a code-breaker at Bletchley Park during World War II.


Early years[edit]

Joan Clarke was born on 24 June 1917 in West Norwood, London. She attended Dulwich High School and went on to gain a double first in Mathematics at Newnham College, Cambridge.[1]

Work at Bletchley Park[edit]

In June 1940 she was recruited by the Government Code and Cypher School (GC&CS) to work at Bletchley Park. She worked in the section known as Hut 8, and quickly became one of the practitioners of Banburismus, a cryptanalytic process developed by Alan Turing which reduced the need for bombes. Hugh Alexander, head of Hut 8 from 1943 to 1944, described her as "one of the best Banburists in the section".[2] She became deputy head of Hut 8 in 1944.[2][3]

Relationship with Alan Turing[edit]

Clarke and fellow code-breaker Alan Turing became very good friends at Bletchley Park. Turing would arrange their shifts so they could be working together, as well as spending a lot of their free time together. In the spring of 1941, Turing proposed marriage to Clarke and subsequently introduced her to his family. After admitting his homosexuality to his fiancé, who was reportedly "unfazed" by the revelation, Turing decided that he could not go through with the marriage and he broke up with Clarke in the summer of 1941.[4][5]

After the war[edit]

At the end of World War II, GC&CS became GCHQ. At GCHQ, Clarke met John "Jock" Murray and they married in 1952. Shortly after, the couple left GCHQ due to Jock's ill health, and moved to Crail, Fife. There they researched history and especially Scottish coinage of the 16th and 17th centuries. They returned to GCHQ in 1962, Jock retiring in 1971 and Joan in 1977.[6][7]

In 1986, following Jock's death, Joan moved to Headington, near Oxford, where she continued her research into coinage. In the 1980s, she also assisted historians studying war-time code breaking at Bletchley Park. However, because of continuing secrecy amongst cryptanalysts, the full extent of her accomplishments remains unknown.[6]


Clarke was awarded an MBE in 1947.[1]


  1. ^ a b Erskine, Ralph. "Murray [Clarke], Joan Elisabeth Lowther (1917–1996)". Oxford Dictionary of National Biography, Oxford University Press. Retrieved 27 October 2013. 
  2. ^ a b Burman, Annie. "Gendering decryption – decrypting gender The gender discourse of labour at Bletchley Park 1939–1945". Retrieved 27 October 2013. 
  3. ^ "Women Codebreakers". Bletchley Park Research. Retrieved 3 November 2013. 
  4. ^ Leavitt, David (2007). The man who knew too much: Alan Turing and the invention of the computer. Phoenix. pp. 176–178. ISBN 978-0-7538-2200-5. 
  5. ^ Grime, James (24 July 2014). "An Alan Turing expert watches the “The Imitation Game” trailer". The Aperiodical. Retrieved 28 July 2014. 
  6. ^ a b Lord, Lynsey Ann (2008). "Joan Elisabeth Lowther Clarke Murray". honours project. University of St Andrews. Retrieved 5 November 2013. 
  7. ^ Stewart, Ian (1986). "Obituary : Lieutenant-Colonel J.K.R. Murray". British Numismatic Journal (British Numismatic Society) 56: 201–203. Retrieved 5 November 2013.