Authors: Gordon Corera
Admiralty clerk John Vassall was caught in a âcompromising situation' in Moscow and blackmailed over his homosexuality. He would spend years passing British secrets before being caught, partly thanks to leads from Anatoly Golitsyn. (Corbis)
Greville Wynne arriving back in Britain after being released as part of a âspy-exchange' between Britain and the USSR. (Getty)
No man's land in Berlin: the moment in when Greville Wynne was exchanged for Gordon Lonsdale.
Kim Philby (left) with George Blake (right) in the Soviet Union. The two former MI6 officers had not known each other in Britain when they were both spying for the KGB. They were only briefly friends in Moscow before they fell out, although Blake did introduce Philby to his last wife, Rufina.
Gordon Lonsdale, whose real name was Konon Molody, worked as an undercover KGB officer, or âillegal', in Britain until he was caught. (Getty)
Oleg Gordievsky preparing for an orienteering competition at a KGB holiday resort near Moscow in 1971. Gordievsky soon became one of MI6's most important agents.
Gordievsky (left) working the diplomatic circuit in Copenhagen and talking to the Danish Defence Minister. He was first approached by MI6 in Denmark although there were initial fears that he might be a double agent.
Oleg Gordievsky, Mikhail Lyubimov and their wives in Denmark. Gordievsky and fellow KGB officer Lyubimov were close friends until Gordievsky fled Moscow.
Ahmed Shah Massoud, known as the Lion of the Panjshir for his guerrilla war against the Soviet Union. MI6 built up close relations with him and sent undercover teams to train and support his fighters. (Getty)
Two future director generals of MI5, Stephen Lander and Eliza Manningham-Buller, shortly after they joined the service. They are pictured on a training course on the roof of a Security Service building on Gower Street.
Despite the reservations of her father (who had prosecuted George Blake), Eliza Manningham-Buller joined MI5 and worked on the Gordiesvky case and was later the head of the Security Service at the time of the 7 July 2005 attacks.
Sir Richard Dearlove, Chief of the Secret Service from 1999 to 2004, pictured after giving evidence into the inquest into the death Diana, Princess of Wales, in 2008. Dearlove led MI6 through the aftermath of the 11 September attacks and the Iraq war. (Getty)