Gordon Welchman

Mathematician, head of Hut 6 at Bletchley Park and, from 1943, Assistant Director for Mechanisation. Born on 15 June 1906 at Fisherton Anger, Wiltshire, the son of a clergyman. He taught mathematics at Sidney Sussex College, Cambridge, and was recruited to Bletchley Park in September 1939. He led Hut 6, which worked on the army and air force Enigma — the bulk of German military signals. His contribution was twofold. Technically, the diagonal board for Turing's Bombe: a refinement that cut false stops by an order of magnitude and turned a promising machine into a working one. Organisationally, he was the first to see that codebreaking had to become a production line rather than a craft — interception, registration, traffic analysis, decryption, translation, distribution. He set this out in a 1941 memorandum, and on that model Bletchley Park grew from a few dozen people to nearly ten thousand. He argued separately for the value of traffic analysis: studying the shape of the enemy's radio network independently of message content. That allowed the order of battle to be reconstructed even when the cipher was not being read. He was appointed OBE. After the war he moved to the United States and worked in defence electronics. In 1982 he published The Hut Six Story, the first detailed account from the inside. It cost him his security clearance and drew official displeasure on both sides of the Atlantic. He died on 8 October 1985.