Sir Arthur Bonsall KCMG CBE, often known as Bill Bonsall was born on 25th June 1917. He served as Director of GCHQ between 1973 to 1978. His predecessor was Joe Hooper, who had left in 1973 to become Cabinet Office Intelligence Co-ordinator. Bonsall's successor was Brian Tovey.
Bonsall went to school at Bishop's Stortford College, and then studied modern languages at St Catharine's College, Cambridge. In 1939 he was accepted for training as an officer in the Herts and Beds Infantry regiment but was then rejected on medical grounds. Through Martin Charlesworth's recruiting system he was then diverted to join the Government Code and Cypher School at Bletchley Park on account of his languages.
In 1940 Bonsall joined the German Air Section under Josh Cooper, studying the Luftwaffe. In 1942 he helped to create a series of daily reports known as the "BMP" (from the initials of its three co-creators, Bonsall, Moyes and Prior). Much of the material was clear voice-traffic and so not encoded. Other material was derived from low-grade codes and were issued at Secret Pearl level. Later reports included information from Luftwaffe Enigma traffic and were issued at Top Secret Ultra level. They dealt with the operations of the Luftwaffe defensive organisation and assisted the Allied Air Commands to design their tactics. Bonsall also spent some time at the RAF Y station at Cheadle.
After the war Bonsall stayed on and for a while he headed GCHQ's prestigious J-Division which handled sigint on the Soviet Union. He was knighted in 1977. He has published an essay on wartime sigint and the RAF in the journal Intelligence and National Security.