During World War II, Britain enjoyed spectacular success in the secret war between hostile intelligence services, enabling a substantial and successful expansion of British counter-espionage. Hugh Trevor-Roper's experiences working for the Secret Intelligence Service (MI6) during the war had a profound impact on him and he later observed the world of intelligence with particular sharpness. To him, the subject of wartime espionage was as worthy of profound investigation and reflection as events from the more distant past. Expressing his observations through some of his most ironic and entertaining prose, Trevor-Roper wrote with a freedom he could not express publicly due to the Official Secrets Act. Based on previously unpublished material - including an extraordinary and previously-unseen correspondence with the exiled spy Kim Philby - this book is a sharp, revealing and personal first-hand account of the intelligence world in World War II and its aftermath.