Joan Clarke, English Cryptanalyst during WWII
By: Rs Staff
Tags: Women in STEM, History, Cryptography, World War II, Empowerment

Joan Clarke was born on June 24, 1917 in London, England to parents William and Dorothy Clarke, and she grew up with three brothers and a sister. Joan had an average childhood and studied maths in Newnham College, Cambridge; however, Cambridge didn’t admit women to full membership of the body academic until post-Second World War, so she was only given the title of Wrangler. Joan was also awarded the Phillippa Fawcett prize (1937) and the Helen Gladstone scholarship (1939–40) for her works in the field of mathematics.

At the start of World War II, mathematicians were recruited from all over the United Kingdom to decypher Nazi messages, which were sent out on radios. The Nazis used encryption devices called Enigma machines, where the chance of decoding the message was an astonishing 150 trillion to one.

‘codebreaking’

Gordon Welchman, one of Joan’s tutors, and four other students set up a project at Bletchley Park to start decoding these Nazi messages. Welchman recruited his old students, and Clarke stood out as a female in the group. She began studying at GCCS (Government Code and Cypher School), which was set up for the main purpose of trying to decipher these messages, as part of Hut 8. The British government wanted to create a method where there was less need for bombes (an electromechanical device as used by British cryptologists).

Hut 8 Team

Despite her reputation as a strong feminist figure today, she was quite traditional, shy, and quiet but nevertheless persistent because she was doing the work that she loved. It was only when she went to work at Bletchley Park that she felt comfortable and was treated as equal. The team of men at GCCS who she worked closely with were progressive in their views surrounding gender roles, and some of them helped her to get her a pay raise equal to theirs. A promotion to the position of Linguist Grade was created and given to Joan, so she could get a raise even though she did not actually speak any other language.

During the beginning stages of the training process, she was the first member of the small group “The Girls” in GCCS, who mainly did routine clerical work. Joan said that there was only one other female member in that team that was also a cryptanalyst.

Clarke soon became skilled with the Banburismus method, created by Alan Turing in the mid-1940s to help decode German messages, and she was said to have stayed over time just to see the results of the different tests she worked on. Her work was vital in driving progress with Banburismus and was in breaking the main Naval Enigma Cipher, which she devoted a lot of her time and effort to. There were many levels and processes involved in what they were working on at Bletchley Park, and after spending a long time on Banburismus, Joan invented the second stage to speed up this routine decryption method. However, her name was never attached to it, and it was not until decades later when Leslie Yoxall claimed that he only created the first stage that Joan was finally given credit for her work.

There were controversies surrouding Clarke’s relationship with Turing, which detracted from their accomplishments, because he had ‘homosexual tendencies.’ They were first engaged in 1941 before mutually breaking off the engagement later on and staying close friends until he passed.

At the end of the war, bombes were more widely available, and so the Banburismus attack was officially cancelled. The team disbanded, and the members all walk different paths in life. Clarke was the successor of both the GCCS and the GCHQ (Government Communications Headquarters), where she met her husband, Lieutenant-Colonel Murray, who she later moved to Scotland with. In 1947, she was appointed the title of ‘a Member of the British Empire’ for her code-breaking work, also known as an MBE. Clarke lived the rest of her life peacefully with her husband until she passed in 1996 from natural causes.

by Ha Nguyen

References

Lord, Lindsay. Joan Elisabeth Lowther Clarke Murray. Mac Tutor. Jul. 2008, https://mathshistory.st-andrews.ac.uk/Biographies/Clarke_Joan/

Flapan, Erica. “100 years ago: Joan Clarke”. Notices of the AMS, vol. 64, no. 3, 2017, pp. 252–55, https://www.ams.org/journals/notices/201703/rnoti-p252.pdf

Joan Clarke. School History. https://schoolhistory.co.uk/notes/joan-clarke/

Joan Clarke. History of Scientific Women. https://scientificwomen.net/women/clarke-joan-158

Women Codebreakers. Bletchley Park Research https://www.bletchleyparkresearch.co.uk/research-notes/women-codebreakers/

Joan Clarke. Spartacus education.https://spartacus-educational.com/Joan_Clarke.htm

Joan Clarke: Mathematics is Not Just a Matter for Men. Vicentia. https://wearevicentia.com/pages/joan-clarke