The "Mitrokhin Archive" is a collection of handwritten notes which were secretly made by the KGB archivist Vasili Mitrokhin during the thirty years in which he served as a KGB archivist in the foreign intelligence service and the First Chief Directorate. When he defected to the United Kingdom in 1992, he brought the archive with him, in six full trunks. His defection was not officially announced until 1999.
The official historian of MI5, Christopher Andrew, wrote two books, The Sword and the Shield (1999) and The World Was Going Our Way: The KGB and the Battle for the Third World (2005), based on material in the archives. The books purport to provide details about many of the Soviet Union's clandestine intelligence operations around the world. They also provide specifics about Guy Burgess, a British diplomat with a short career in MI6, said to be frequently under the influence of alcohol; the archive indicates that he gave the KGB at least 389 top secret documents in the first six months of 1945 along with a further 168 in December 1949.
In July 2014, the Churchill Archives Centre at Churchill College released Mitrokhin's edited Russian-language notes for public research. The original handwritten notes by Vasili Mitrokhin are still classified.