A spy whose intel backed the world away from nuclear war has died

Oleg Gordievsky was a top Russian KGB officer who had a growing disillusionment with the Soviet Union after the Prague Spring in 1968. Eventually, he was recruited by the British spy agency, MI6, where Gordievsky became one of the West's most important double agents. Ben Macintyre is an author who interviewed Gordievsky extensively, and explains what made him an exception in the history of intelligence and spycraft.