Professor Christopher Andrew, author of ‘The Defence of the Realm: The Authorized History of MI5’, introduces highlights of the 29th release of Security Service records to The National Archives. Among the 77 files released are the ten post-war diaries of Guy Liddell, then Deputy Director General of MI5. The diaries’ entries dramatically convey the tensions of the early Cold War and cover the period from 1945 to 1953. Professor Andrew also discusses other notable files in the latest release including the mysterious disappearance of a Catholic priest and a famous veteran of the Spanish Civil War. This release brings the total number of Security Service records held at The National Archives to 5,003.