Mitrokhin first offered his material to the US' Central Intelligence Agency (CIA) in Latvia but they rejected it as possible fakes.

Mitrokhin sometimes dated the beginnings of his disillusionment to Nikita Khrushchev's famous speech to the Communist Party of the Soviet Union congress denouncing Joseph Stalin, though it seems he may have been harbouring doubts for some time before that.

For years, he had listened to broadcasts on the BBC and Voice of America, noting the gulf between their reports and party propaganda.

After the dissolution of the Soviet Union in 1991, he traveled to Latvia with copies of material from the archive and walked into the American embassy in Riga.

Richard Tomlinson, the MI6 officer imprisoned in 1997 for attempting to publish a book about his career, was one of those involved in retrieving the documents from containers hidden under the floor of the dacha.

[6] The notes given by Mitrokhin to the MI6 revealed exposures about some unknown number of Soviet agents, including Melita Norwood.