The Cambridge Spies continue to fascinate - but one of them, John Cairncross, has always been more of an enigma than the others. He worked alone and was driven by his hostility to Fascism rather than to the promotion of Communism. During his war-time work at Bletchley Park, he passed documents to the Soviets which went on to influence the Battle of Kursk. Geoff Andrews gained exclusive access to the Cairncross papers and secrets, and has spoken...