The Secret intelligence Service was created in 1909 and this comprehensive account covers the organisation's history throughout both world wars, describing in hithero unpublished detail clandestine operation conducted under the direction of the first three Chiefs: Captain Mansfield Smith-Cumming, Admiral Hugh Sinclair and Colonel Stewart Menzies. The names of hundreds of intelligence officers and their agents are identified, together with previously undisclosed documents revealing the scale of the semi-transparent network of Passport Control Offices which stretched across the globe, enabling SIS personnel to conduct espionage.

The silver Gestapo warrant forged by MI6 to help Hans Bernd Gisevius escape to Switzerland from Berlin after the failure of the bomb plot to kill Hitler on 20 July 1944.