- Sep 22, 2023
- 2 min read

Cryptanalyst – Code-breaker: Joan Clarke

Updated: Feb 8

Hello everyone! I'm Tina and this is Women Weekly, where I post about one wonderful woman in the STEM field every Friday. This week I wrote about an incredible cryptanalyst who saved many lives during WWII – Joan Clarke.

Joan Clarke was born in 1917 in London as the youngest of 5 siblings. She graduated from Dulwich High School for Girls and won a scholarship to attend Newnham College, Cambridge. She studied mathematics and performed exceptionally well, but that wasn't enough to get her a full degree, since those were only given to men at the time. When World War II started, Gordon Welchman, her academic supervisor, recruited her to the Government Code and Cypher School (GCCS), where she contributed to breaking the German Enigma Code. After the war ended, she worked in the Government Communication Headquarters (GCHQ), where she met her future husband John Murray. Because of his illness, the couple moved to Scotland for several years. Thanks to Murray, Joan earned an interest in coinage and was even awarded by the British Numismatic Society for her works about Scottish gold unicorn coins. She later spent her time providing information about the codebreaking during WWII to historians and continued her studies of numismatics until her death in 1996.

When Joan arrived in Bletchley Park, where the GCCS was residing, she was placed to work with 'The Girls' – an all-women group completing clerical duties but was soon moved to Hut 8, a team focusing on breaking the German Naval Enigma Code led by Alan Turing. Their main task was helping electrotechnical decyphering machines or 'bombes' come to answers quicker with a practice called Bamburismus.

Joan soon became one of its best practitioners and as a recognition of her workload, she started receiving Linguist Grade pay to make up for the sexist wage gap, even though she couldn't speak any foreign languages. In 1941, the team got their hands on German cypher equipment and was able to lower the number of German convoy attacks (a.k.a. wolf packs) on Allies' shipping drastically. Joan made it to being deputy head of the team and over time became quite close with Turing. They were engaged for a brief period but decided to just remain friends because of Turing's homosexuality.

Joan Clarke was one of the very few women working on breaking the German Enigma Code and a very important one at that. Sadly, she gets very little recognition for her outstanding contributions. After the war ended, all evidence of the code-breaking at Bletchley Park was destroyed, which only further covered the outstanding intelligence of Joan Clarke.