John Croft, a centenarian British codebreaker who played a significant role at Bletchley Park during the Second World War and later pioneered crime survey research in the United Kingdom, has died at the age of 103. Born Ivor John Cohen on January 6, 1923, in Brondesbury, north London, he changed his surname with his family to Croft in the 1930s.

A graduate of Christ Church, Oxford, where he read history, Croft was recruited into intelligence work in 1942. Following training at the Government Code and Cypher School in Bedford, he was assigned to Hut 15A at Bletchley Park. There, he worked in the “Testery,” headed by Major Ralph Tester, focusing on deciphering Tunny—the codename for the German Lorenz cipher used by the High Command. The team relied on labor-intensive manual methods to decrypt messages, including one that revealed Adolf Hitler’s order for the arrest of the Yugoslav partisan leader Draža Mihailović, offering a substantial gold reward.

In 1943, Croft transferred to the Government Communications Bureau (MI6) in London, where he engaged in monitoring Soviet and Comintern cryptographic communications. This operation was a sensitive task, especially given the complicity of Soviet espionage within British intelligence ranks. Croft later suspected that the notorious double agent Kim Philby may have been involved in compromising his unit.

After the war, Croft returned to Oxford to complete his degree and subsequently trained as a teacher. He entered the civil service in 1951 as an inspector in the Home Office children’s department. His interest in criminology led him to pursue a master’s degree focused on juvenile delinquency. By 1966, Croft had joined the Home Office research unit, eventually becoming its head from 1972 to 1983.

Croft played a critical role in addressing concerns about the reliability of police-recorded crime statistics in the late 1970s. Under his leadership, the first British Crime Survey was launched in 1982. Now known as the Crime Survey for England and Wales (CSEW), it provides a robust and independent measure of crime trends, widely regarded as more accurate than official police data.

In addition to his governmental work, Croft engaged with the international criminology community, including leadership roles with the Council of Europe’s Criminological Scientific Council and the International Congress on Criminology.

Beyond his public service, Croft was a dedicated artist. A self-taught painter inspired by abstract expressionism, he exhibited widely from the 1960s onward. His work featured in group and solo exhibitions, including the 1967 Survey ’67 show at Camden Arts Centre and later presentations at Sussex and Warwick universities. Even after retiring to the Isle of Man and then Bath, Croft continued to produce and exhibit his minimalist, landscape-derived paintings, with his art held in collections at Oxford, Cambridge, and the London School of Economics.

Croft was appointed Commander of the Order of the British Empire (CBE) in 1982 and was predeceased by his partner, Ray Kelly. He passed away on July 12, 2026.