A former KGB double agent has identified the long-secret "Fifth Man" in a notorious Soviet spy ring as John Cairncross, a former British intelligence officer.

Oleg Gordievsky, a career KGB agent who worked for the British as a double agent before escaping to the West in 1985, disclosed the man's identity in "KGB: The Inside Story," a new book excerpted Monday in The Times newspaper. It was written with Christopher Andrew.The identity of the "Fifth Man" has been speculated for years, and a number of people have been suspected, including Cairncross.

Gordievsky said Cairncross played an important part in the spy ring led by Harold "Kim" Philby and including Guy Burgess, Donald Maclean and Anthony Blunt.

Philby, said to be the most damaging double agent in British history, spied for the Soviets for 26 years until he defected to Moscow in 1963. Philby rose to become head of the anti-Soviet section of M16, the British service responsible for gathering foreign intelligence.