Joan Clarke

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.

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.

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.

In June 1940, Welchman recruited Clarke to the agency.

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.

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.

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.

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.

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.

After the war, Clarke worked for Government Communications Headquarters (GCHQ).

Hugh Alexander, head of Hut 8 from 1943 to 1944, described her as "one of the best Banburists in the section".

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".

Clarke became deputy head of Hut 8 in 1944, although she was prevented from progressing because of her sex, and was paid less than the men.

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.

There, in 1947, she met Lieutenant-Colonel John Kenneth Ronald Murray, a retired army officer who had served in India.

She was denied a full degree, as until 1948 Cambridge awarded these only to men.

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.

They were married by the Bishop of Chichester on 26 July 1952 in Chichester Cathedral, where her father was a Canon.

Shortly after their marriage, John Murray retired from GCHQ due to ill health and the couple moved to Crail in Fife where they lived at Priorscroft, 14 Nethergate.

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.

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.

They returned to work at GCHQ in 1962 where Clarke remained until 1977 when she retired aged 60.

During the 1980s, she helped Sir Harry Hinsley with the appendix to volume 3, part 2 of British Intelligence in the Second World War.

She also helped historians studying war-time codebreaking at Bletchley Park.

Following her husband's death in 1986, Clarke moved to Headington, Oxfordshire, where she continued her research into coinage.