Geoffrey Prime (born 1938) is a British former spy for the Soviet Union while working for the Royal Air Force and later for Government Communications Headquarters (GCHQ), the British cryptography agency, during the 1960s and 1970s. He was eventually convicted for espionage as well as for child sexual abuse.
Prime was first detected when his wife persuaded him to turn himself in, and he later participated in the Paedophile Information Exchange, a pro-paedophile activism group being watched by the British government. Members of the group used secret codes to communicate. He was subsequently identified as supplying information to the Soviets, and was tried, convicted, and imprisoned in 1982. His defence counsel was George Carman QC. He was sentenced to a total of 38 years, 35 for offences under section 1 of the Official Secrets Act 1911 and 3 for sex offences against children. The information he disclosed was publicly represented as having been damaging to the UK and beneficial to the Soviets, but details were not released. His position at GCHQ made him privy to information which would have been damaging had he turned it all over to the Soviets.
His sentence was the second-longest jail sentence in British legal history. The judges at his trial and his appeal said that if Britain had been at war with the Soviet Union, his crimes would make him eligible for the death penalty — it remained the punishment for treason until the Human Rights Act of 1998 — and that they would have had no compunction about imposing it. He was released from prison in 2001. He currently lives quietly in an originally undisclosed area, though The Daily Mail has released some information of his whereabouts. He was released on licence, but the parole board also decided that his name remains on the sex offenders register.
In 2009 it was revealed that Prime had told the KGB that the United Kingdom and the United States had cracked high-level Soviet codes. As a result, the Soviet government changed them, making their military ciphers unreadable by the UK and US until the end of the Cold War.
Further reading 
- Cole, D. J. Geoffrey Prime: The Imperfect Spy.