When an elderly man with a battered suitcase walked into the British embassy in Vilnius in 1992, few could have guessed what he was about to hand over. Gordon Corera tells the story of Vasili Mitrokhin, an under-the-radar Soviet archivist who copied thousands of classified KGB documents over 12 years. Speaking to Elinor Evans, he reveals how a project that began as a private rebellion against the agency he once served evolved into one of the greatest intelligence coups of the 20th century. {listen}