Dubbed an 'agent of British imperialism' by Joseph Stalin, Reginald Teague-Jones (1889- 1988) was the quintessential English spy whose exceptional story is recounted in this new biography. He studied in St Petersburg, participated in the 1905 Revolution and spent the rest of his life working for various branches of British secret intelligence. Plunging into the Great Game, he participated in daring operations against the Bolsheviks and tracked down a turbulent German agent, Wilhelm Wassmuss, who was spreading anti-British propaganda in Persia. Teague-Jones was also held responsible for the execution of 'the 26 Commissars' after the fall of the Baku Commune in 1918. This became one of the Soviet Union's most powerful cults of martyrology, inspiring a poem by Yesenin, a Brodsky painting, a 1933 feature film and an immense monument. Shortly after, Teague-Jones changed his name to Ronald Sinclair and adopted a secret persona for the next five decades, part of which he worked undercover in the United States as an expert on Indian, Soviet and Middle-Eastern affairs, possibly in collaboration with the OSS, the new American secret service. In his swan song in espionage he kept a gimlet eye on the Soviet delegation to the UN in New York. For these reasons, and many others besides, Reginald Teague-Jones is the most important British spy you have never heard of.