: The files unmasked hundreds of "illegal" sleeper agents, including Melita Norwood , Britain's longest-serving Soviet spy, and exposed elaborate sabotage plans against Western infrastructure like power grids and dams.

The Sword and the Shield: The Mitrokhin Archive and the Secret History of the KGB

: Much of the material is now physically housed at the Churchill Archives Centre at Churchill College, Cambridge, for public research. Key Publications and Research Materials

Vasili Mitrokhin spent 12 years (1972–1984) secretly copying classified KGB documents by hand while working as the chief archivist for the Soviet foreign intelligence directorate. Disillusioned by the regime, he hid these notes in milk churns beneath his family dacha before defecting to the United Kingdom.