Ben Macintyre, author of a book about the double agent, “The Spy and the Traitor,” told the BBC that Gordievsky managed “in a secret way to launch the beginning of the end of the Cold War.” ...

He was the most senior Soviet spy to defect during the Cold War. Documents declassified in 2014 showed that Britain considered Gordievsky so valuable that Thatcher sought to cut a deal with Moscow ...