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. Now, Geoff Andrews has access to the Cairncross papers and secrets, and has spoken to friends, relatives and former colleagues.

A complex individual emerges – a scholar as well as a spy – whose motivations have often been misunderstood. After his resignation from the Civil Service, Cairncross moved to Italy and here he rebuilt his life as a foreign correspondent, editor and university professor.

This gave him new circles and friendships – which included the writer Graham Greene – while he always lived with the fear that his earlier espionage would come to light. The full account of Cairncross's spying, his confession and his dramatic public exposure as the 'fifth man' will be told here for the first time, while also unveiling the story of his post-espionage life.