During the decade that culminated in the rise to power of Mikhail Gorbachev, an avalanche of top secret documents poured out from KGB headquarters in Moscow to its residencies throughout the world. Oleg Gordievsky was a KGB colonel and Resident-designate in London in 1985 when he defected; it was later revealed that he had been working as a double agent for British intelligence since 1974, regularly risking his life by passing copies of KGB documents to the British. This volume is a revealing selection of this highly classified material, with an informative commentary by Christopher Andrew, based on joint analysis of the documents with Gordievsky.