Joan Clarke

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Joan Clarke

Clarke, c. 1940s
Joan Elisabeth Lowther Clarke

(1917-06-24)24 June 1917
West Norwood, London, England, UK
Died4 September 1996(1996-09-04) (aged 79)
Headington, Oxfordshire, England, UK
Other namesJoan Clarke Murray (1952–1996)
Alma materNewnham College, Cambridge
Known forCodebreaking at Bletchley Park in World War II
John Murray
(m. 1952; died 1986)
PartnerAlan Turing (engaged in 1941 but did not marry)
AwardsBritish Numismatic Society Sanford Saltus Gold Medal (1986)

Joan Elisabeth Lowther Murray, MBE (née Clarke; 24 June 1917 – 4 September 1996) was an English cryptanalyst and numismatist who worked as a code-breaker at Bletchley Park during the Second World War. Although she did not personally seek the spotlight, her role in the Enigma project that decrypted the German secret communications earned her awards and citations, such as appointment as a Member of the Order of the British Empire (MBE), in 1946.[1][2]

Early life[edit]

Joan Elisabeth Lowther Clarke was born on 24 June 1917 in West Norwood, London, England. She was the youngest child of Dorothy (née Fulford) and the Revd William Kemp Lowther Clarke. She had three brothers and one sister.[3]

Clarke attended Dulwich High School for Girls in south London and won a scholarship in 1936, to attend Newnham College, Cambridge. Her work in an undergraduate Geometry class at Cambridge drew the attention of mathematician Gordon Welchman, who became her academic supervisor.

Clarke gained a double first degree in mathematics and was a Wrangler.[4][5] She was denied a full degree, as until 1948 Cambridge awarded these only to men.[1]


Codebreaking at Bletchley Park[edit]

Just before the outbreak of World War II, Welchman and three other top mathematicians were recruited to the Government Code and Cypher School (GC&CS), which aimed to break the German Enigma Code. The Germans used the Enigma machine to encrypt their messages, which they believed unbreakable.

In June 1940, Welchman recruited Clarke to the agency.[6][3] She arrived at Bletchley Park on 17 June 1940 and was initially placed in an all-women group, referred to as "The Girls", who mainly did routine clerical work. Clarke said she knew of only one other female cryptologist working at Bletchley Park.[3]

Clarke worked at Bletchley Park in the section known as Hut 8 and quickly became the only female practitioner of Banburismus, a cryptanalytic process developed by Alan Turing which reduced the need for bombes: electromechanical devices as used by British cryptologists Welchman and Turing to decipher German encrypted messages during World War II.[7] Clarke's first work promotion was to Linguist Grade which was designed to earn her extra money despite the fact that she did not speak another language. This promotion was a recognition of her workload and contributions to the team.[3]

In 1941, trawlers were captured as well as their cipher equipment and codes. Before this information was obtained, wolf packs had sunk 282,000 tons of shipping a month from March to June 1941. By November, Clarke and her team were able to reduce this number to 62,000 tons.[8] Hugh Alexander, head of Hut 8 from 1943 to 1944, described her as "one of the best Banburists in the section".[9][page needed] Alexander himself was regarded as the best of the Banburists. He and I. J. Good considered the process more an intellectual game than a job. It was "not easy enough to be trivial, but not difficult enough to cause a nervous breakdown".[10][full citation needed]

External videos
video icon Murray née Clarke talking about her engagement to Turing

Clarke became deputy head of Hut 8 in 1944,[9][11] although she was prevented from progressing because of her sex, and was paid less than the men.[3] Clarke and Turing had been close friends since soon after they met, and continued to be until Turing's death in 1954. They shared many hobbies and had similar personalities.[1] They became very good friends at Bletchley Park. Turing arranged their shifts so they could work together, and they also spent much of their free time together. In early 1941, Turing proposed marriage to Clarke, and subsequently introduced her to his family. Although he privately admitted his homosexuality to her—she was reportedly unfazed by the revelation—Turing decided that he could not go through with the marriage, and broke up with Clarke in mid-1941. Clarke later admitted that she suspected Turing's homosexuality for some time, and it was not much of a surprise when he made the admission to her.[12][13]

After the war[edit]

After the war, Clarke worked for Government Communications Headquarters (GCHQ). There, in 1947, she met Lieutenant-Colonel John Kenneth Ronald Murray, a retired army officer who had served in India. They were married by the Bishop of Chichester on 26 July 1952 in Chichester Cathedral, where her father was a Canon.[12][13] Shortly after their marriage, John Murray retired from GCHQ due to ill health and the couple moved to Crail in Fife[5] where they lived at Priorscroft, 14 Nethergate.[14] They returned to work at GCHQ in 1962 where Clarke remained until 1977 when she retired aged 60.[3][15]

Following her husband's death in 1986, Clarke moved to Headington, Oxfordshire, where she continued her research into coinage. During the 1980s, she helped Sir Harry Hinsley with the appendix to volume 3, part 2 of British Intelligence in the Second World War.[4] She also helped historians studying war-time codebreaking at Bletchley Park. Due to continuing secrecy among cryptanalysts, the full extent of her accomplishments remains unknown.[3]

Numismatic interest[edit]

After meeting her husband, who had published work on the Scottish coinage of the 16th and 17th centuries, Clarke developed an interest in numismatics history.[8] She established the sequence of the complex series of gold unicorn and heavy groat coins that were in circulation in Scotland during the reigns of James III and James IV. In 1986, her research was recognised by the British Numismatic Society when she was awarded the Sanford Saltus Gold Medal. Issue No. 405 of the Numismatic Circular described her paper on the topic as "magisterial".[4][16]


On 4 September 1996, Clarke died at her home at 7 Larkfields, Headington Quarry.[3] An Oxfordshire Blue Plaque was unveiled on her house on 27 July 2019.[17]

Portrayal in adaptation[edit]

Clarke was portrayed by Keira Knightley in the film The Imitation Game (2014), opposite Benedict Cumberbatch as Alan Turing.[18][19] Turing's surviving niece, Inagh Payne, described Clarke as "rather plain" and thought that Knightley was inappropriately cast as Clarke.[20] Turing biographer Andrew Hodges also criticised the film, stating the script "built up the relationship with Joan much more than it actually was".[19]

The portrayal of Clarke, by Amanda Root, in the 1996 film Breaking the Code, is a much truer depiction, both of the woman and her relationship with Turing. [21]

In contrast, an article by BBC journalist Joe Miller said that Clarke's "story has been immortalised". Director Morten Tyldum said the film shows how Clarke succeeded in her field despite working in a time "when intelligence wasn't really appreciated in women".[1]

Knightley was nominated for the Academy Award for Best Supporting Actress at the 87th Academy Awards for her performance as Clarke.[22]


  1. ^ a b c d Miller, Joe (10 November 2014). "Joan Clarke, woman who cracked Enigma cyphers with Alan Turing". BBC News.
  2. ^ "No. 37412". The London Gazette (Supplement). 28 December 1945. p. 290.
  3. ^ a b c d e f g h Lord, Lynsey Ann (2008). "Joan Elisabeth Lowther Clarke Murray". Honours project. University of St Andrews. Retrieved 5 November 2013.
  4. ^ a b c Erskine, Ralph (2004). "Murray [Clarke], Joan Elisabeth Lowther (1917–1996)". Oxford Dictionary of National Biography. Vol. 1 (online ed.). Oxford University Press. doi:10.1093/ref:odnb/71791. Retrieved 27 October 2013. (Subscription or UK public library membership required.)
  5. ^ a b Lord Stewartby (1997). "Obituary Mrs J.E.L. Murray" (PDF). British Numismatic Society. Retrieved 15 November 2014.
  6. ^ Anderson, L. V. (3 December 2014). "The Imitation Game: Fact vs Fiction". Slate. Archived from the original on 23 January 2015. Retrieved 3 January 2015.
  7. ^ Welchman, Gordon (2005) [1997], The Hut Six story: Breaking the Enigma codes, Cleobury Mortimer, England: M&M Baldwin, pp. 138–145, ISBN 9780947712341 New edition updated with an addendum consisting of a 1986 paper written by Welchman that corrects his misapprehensions in the 1982 edition.
  8. ^ a b "Joan Elisabeth Lowther Clarke Murray". Retrieved 3 February 2017.
  9. ^ a b Burman, Annie (2013). Gendering Decryption—Decrypting Gender: The Gender Discourse of Labour at Bletchley Park, 1939–1945 [65 pp.] (PDF) (M.A.). Mikael Byström, Thesis Supervisor, Torkel Jansson, Seminar leader, [Seminar date, 4 June 2013]. Uppsala, SWE: Uppsala universitet. Retrieved 14 January 2017.[page needed]
  10. ^ Good (1993) p. 157.[full citation needed]
  11. ^ "Women Codebreakers". Bletchley Park Research. 3 October 2013. Retrieved 3 November 2013.
  12. ^ a b "Births, marriages, and deaths". The Times. 29 July 1952. p. 1.
  13. ^ a b "Index entry". FreeBMD. Office for National Statistics. Retrieved 3 February 2020.
  14. ^ Murray, John (2010). A Crail Scrapbook. Crail: Crail Museum Trust.
  15. ^ Stewart, Ian (1986). "Obituary: Lieutenant-Colonel J.K.R. Murray" (PDF). British Numismatic Journal. 56. British Numismatic Society: 201–203. Archived from the original (PDF) on 16 September 2016. Retrieved 5 November 2013.
  16. ^ "Sanford Saltus Gold Medal". British Numismatic Society. 2013. Archived from the original on 12 November 2016. Retrieved 14 November 2014.
  17. ^ "Joan Murray, née Clarke (1917–1996) Cryptanalyst and numismatist – 7 Larkfields, Headington Quarry, Oxford". UK: Oxfordshire Blue Plaques Board. Retrieved 27 June 2020.
  18. ^ Miller, Joe (10 November 2014). "Joan Clarke played by Keira Knightley in upcoming film". BBC News. BBC. Retrieved 14 November 2014.
  19. ^ a b "Alan Turing's biographer criticises upcoming biopic for downplaying gay identity". 24 June 2013.
  20. ^ Lazarus, Susanna (19 November 2013). "Imitation Game filmmakers accused of romanticising the relationship between Benedict Cumberbatch and Keira Knightley's characters by Alan Turing's niece, Inagh Payne". Radio Times. Retrieved 10 September 2014.
  21. ^ "Breaking the Code". IMDb.
  22. ^ "Oscars 2015: Best supporting actress". BBC News. 23 February 2015. Retrieved on 2019-04-09