Identified as a spy only after he had been arrested on charges of pedophilia in April 1982, having made a confession to his wife Rhona, Prime took nine hours to detail his espionage for the KGB. He had joined the Royal Air Force at the age of 18 in 1956 and, having qualified as a Russian linguist, joined GCHQ in 1968. A decade later, he resigned to work as a taxi driver in Cheltenham, but in the meantime he had sold vast quantities of classified material to his Soviet contacts. When his house was searched, a quantity of incriminating paraphernalia was recovered, including onetime pads and envelopes preaddressed to a contact in East Berlin.
Prime admitted that he had first approached the Soviets while he was at RAF Gatow in Berlin and had remained in touch thereafter, undergoing lengthy debriefings in Vienna in 1980 and Berlin in 1981.
In November 1982 he was sentenced to 35 years’ imprisonment for breaches of the Official Secrets Act and four years for three sexual assaults on children.