Kim Philby (1912-1988) was rewarded with Russian citizenship for his services to the Soviets. He was head of anti-Communist counter-espionage with British intelligence between 1944 and 1946, then became the secretary of the British embassy in Washington. There he worked with the CIA from 1949 to 1951 before jumping ship - literally. He was last seen in 1963, leaping on to a boat bound for Russia from Beirut, Lebanon.
Guy Burgess (1910-1963) worked for the BBC for nearly 10 years from 1936 and during the 1940s joined MI5, where he worked under Philby. In 1950 he was recalled from the US for serious misconduct and subsequently disappeared with fellow spy Donald Maclean. They emerged in the Soviet Union a few years later.
Donald Maclean (1913-1983) joined the diplomatic service straight from Cambridge and was head of the Foreign Office American Department by 1950. That job gave him access to highly classified material on Britain's atomic projects, which he carefully handed over to the Soviets.
Anthony Blunt (1907-1983) was the so-called "fourth man" in the Cambridge spy ring. He acted as a talent-spotter, supplying the names of likely recruits to the Communist cause. During the Second World War he worked for British intelligence but he later defected to the other side. He confessed his involvement in the ring in exchange for immunity from prosecution after Philby defected in 1964. It was not until 1979 that his role became public knowledge and he was stripped of his knighthood and academic honours.
John Cairncross (1913-1982) was recruited by Blunt and introduced to Burgess while still at Cambridge. He joined the Communist Party in 1937 and got a job at the Foreign Office working alongside Maclean. He became useful while working at the Treasury, where he was able to leak details about the military decoding centre at Bletchley Park. His information about British and US atomic weapons was widely suspected of being the foundation of the Soviet nuclear programme.
William Vassall (1924-1996) was blackmailed by the KGB over his homosexuality in 1951 while posted to Moscow and was forced to spy for them in the mid- 1950s while working at the Admiralty. He described himself as a "pygmy" in the spy world next to the Cambridge Five but still served 10 years of an 18-year sentence following his arrest in 1962.
George Blake (born 1922), a naval specialist, worked for the British Intelligence Services from 1944 until 1961 but was also on the payroll of the KGB. When his activities came to light he was given a 42-year prison sentence, but he defected to Russia after escaping from Wormwood Scrubs prison in 1966.
The agents to be revealed this week could be just as unexpected. The finger has been pointed at senior police officers, civil servants, academics and journalists. But there is much speculation, fuelled by the latest revelations, that at least one of the names disclosed will be of a man "prominent in public life" but now dead. Last night, names floating around Westminster included the former prime minister Harold Wilson, long suspected by a group of right-wingers with MI5 connections of being a Soviet agent. Peter Wright alleged in his notorious book Spycatcher that a cohort of intelligence and army officers actively plotted against the then Labour premier.
A close associate of Wilson, the textile tycoon Joseph Kagan, was also the subject of much suspicion. An even more unlikely candidate for outing as a spy is Lord Rothschild, the third baron, a scientist and head of the "think tank" in Edward Heath's Conservative administration between 1971 and 1974. He had been a friend of Blunt at Cambridge and was the focus of speculation, again vigorously denied.
Allegations have also appeared on a regular basis against a number of prominent former Labour politicians, including Tom Driberg, the openly gay former chairman of the party and a CND supporter. It has often been claimed that he was a double agent working for both MI5 and the KGB.
Another name floated is that of John Stonehouse, the disgraced former postmaster general and Labour MP for Walsall North who hit the headlines in 1974 when he disappeared from a Miami beach. At first he was feared drowned but he later surfaced living under an assumed name in Australia. Stonehouse, who was convicted of fraud, strenuously denied until his death that he had been a Czech agent.
Last night, John Symonds, a former Scotland Yard police officer, was being touted as a candidate for "outing". There were claims that he worked for the KGB over a 10-year period. Symonds, who is now believed to be in Portugal, has claimed in the past that the KGB had approached him to supply the names of corrupt Scotland Yard officers.