William Gordon Welchman (known as Gordon) was born in Bristol on 15 June 1906. He held dual British and American citizenship, becoming a naturalised US citizen in 1962. In the 1920s, he studied mathematics at Trinity College, Cambridge before progressing to a research fellowship at Sidney Sussex College. He remained in Cambridge until he was recruited by the Government Code and Cypher School (GCCS, later GCHQ) at the advent of the Second World War. Welchman led Hut Six at Bletchley Park and was responsible for overseeing cryptanalysis work on German Enigma machines.

After 1945, Welchman worked briefly at John Lewis before moving to the United States and teaching the first course on computer coding at the Massachusetts Institute of Technology (MIT) (see WLCH 7). In the 1960s and 1970s, he worked and then consulted at the MITRE Corporation in Massachusetts, where he helped to develop secure communications systems such as JTIDS.

From the mid-1970s onwards, Welchman’s papers show his increasing interest in writing about wartime cryptanalysis. He believed that discussing Bletchley Park (and its equivalent institutions in other Allied nations) was crucial to improving general awareness of communications and intelligence work. Welchman’s research culminated in ‘The Hut Six Story’ (1982), a memoir describing the contribution of his codebreaking team in Hut Six. The book was controversial with both British (GCHQ) and American (NSA) intelligence services, resulting in Welchman losing his security clearances in both countries due to his descriptions of still-classified events. Nevertheless, Welchman continued writing, with two more books planned: one about “the early days of Bletchley” (which he was working on with Robin Denniston), and one about early computer development. However, he did not finish another book before his death on 8 October 1985. His article ‘From Polish Bomba to British Bombe: The Birth of ULTRA’ was published posthumously in 1986.

Welchman married three times: Katharine Hodgson (m. 1937-1959), Fannie Hillsmith (m. 1959-1970), and Elisabeth “Teeny” Huber (m. 1972). He had three children (a son and two daughters) with his first wife.