Ann Katharine Mitchell a British cryptanalyst and psychologist who worked on decrypting messages encoded in the German Enigma cypher at Bletchley Park during the Second World War died on 11 May 2020, aged 97, in Edinburgh. She tested positive for COVID-19 shortly before her death. After the war she became a marriage guidance counsellor, then studied for a Master of Philosophy at the University of Edinburgh. She worked at the university’s Department of Social Administration and wrote several academic books about the psychological effects of divorce on children including Someone to Turn to: Experiences of Help Before Divorce (1981) and Children in the Middle: Living Through Divorce (1985). Ann Williamson was born in Oxford on 19 November 1922, to Herbert Stansfield Williamson and Winifred Lilian Williamson (née Kenyon). Herbert had previously worked in the Indian Civil Service; Winifred had helped organise one of the first family planning clinics in Britain. Williamson gained a scholarship to Headington School, Oxford from 1930 to 1939, before winning a place to study mathematics at Lady Margaret Hall, University of Oxford, between 1940 and 1943. At the time relatively few women went to Oxford and even fewer studied maths. There were only five women in her year at Oxford and she remarked that the men coming to university had been taught maths much better at school than the girls. Indeed, it was suggested to her by the headmistress of her school that studying maths was “unladylike”; her parents had to overrule her school to allow her to take up her place at Oxford. Williamson was recruited to work at Bletchley Park in September 1943 after she graduated from Oxford, and until May 1945 she worked in Hut 6 on German Army and Air Force Enigma decryptions. She was recruited as a temporary worker with the Foreign and Commonwealth Office on an annual salary of £150 (increased to £200 after her 21st birthday). Much of her work involved converting ‘cribs’ into ‘menus’, the operating instructions for the Bombe decryption devices to identify what that day’s Enigma settings might be. After the war, like others who worked at Bletchley, she was instructed to forget about her work there and never to talk about it. Once the work at Bletchley became public and the ban was lifted she gave many illustrated talks and interviews about her wartime role. Her story is included in the book The Bletchley Girls: War, Secrecy, Love and Loss: The Women of Bletchley Park Tell Their Story (2015) by the historian Tessa Dunlop. In the 1950s, she worked as a marriage guidance counsellor with the Scottish Marriage Guidance Council (now known as Relate Scotland). In the 1970s she returned to university to study social policy and in 1980 she graduated with a Master of Philosophy from the University of Edinburgh. In the early 1980s she was research associate at the Department of Social Administration in the University of Edinburgh. She worked and published extensively on the subject of marriage breakup and divorce, and in particular on children’s experience of family breakup. Her books include Someone to Turn To: Experiences of Help before Divorce (1981); When Parents Split Up (1982); Children in the Middle (1985); Coping with Separation and Divorce (1986); and Families (1987). They have been translated into a number of languages. In her seventies, Mitchell researched and wrote about the history of Edinburgh. She published two books, The People of Calton Hill (1993) and No More Corncraiks: Lord Moray’s Feuars in Edinburgh’s New Town (1998). She married John Angus Macbeth Mitchell, known as Angus, on 13 December 1948, they had four children, and lived in Edinburgh. He died in 2018 after retiring as a senior civil servant. During his life in the army, civil service and in the voluntary sector, he was awarded Companion of the Bath, Commander of the Royal Victorian Order and the Military Cross.