From Smithsonian Magazine:
The papers contain names of spies, descriptions of secret weapons and detailed plots against the West
A stash of 2,000 documents smuggled out
of the former USSR is now available for viewing at Cambridge
University. As intelligence historian Christian Andrew told Time,
the documents represent "the most important single intelligence source
ever," listing the names of around 1,000 spies who operated in the
U.S., designs for various booby traps and weapons and plots that were
later given names such as "the Mousetrap."
The documents have been held in secret since Vasili Mitrokhin, a
former KGB official-turned-dissident, snuck them out of the collapsed
Soviet Union in 1992. Mitrokhin first tried bringing them to a U.S.
embassy in Latvia. (Time writes that the Americans turned him away; the Guardian states
that it was actually the long lines at the embassy that deterred
him.) He next tried the British embassy, which was more receptive.
Mitrokhin was taken to Britain to continue life under a new name and
identity, and since then the classified documents have been stashed in
19 boxes at an archive in Cambridge, Time writes.
Over the years, the papers have proven especially useful for
identifying former spies and for offering insight into some of the
USSR's troubles with its embedded intelligence officers. One British spy
who was recruited to work for the Soviets was “constantly under the
influence of alcohol,” while another was “not very good at keeping
secrets,” Time reports....MORE
HT:
The Verge