Reginald Teague-Jones MBE (30 July 1889 – 16 November 1988) was a British political and intelligence officer. He was active in the Caucasus and Central Asia during the Russian Civil War. For the last 66 years of his life he was known as Ronald Sinclair.
Teague-Jones was born in Lancashire. He was brought up in the former Russian capital, St Petersburg. His father was a language teacher and died when Reginald was still a child. He was educated at a German-run school that specialized in languages where he learned French, German and Russian, and at Bedford School between 1905 and 1907. He later spent two years studying at King's College London, but left without taking a degree.
In 1910, at the age of 21, he joined the Indian Police and was soon transferred to the (British) Indian government's Foreign and Political Department, an organization that had trained earlier players in the so-called Great Game, the clandestine struggle for influence in Central Asia between the Russian and British empires during the 19th and early 20th centuries.
Here he became involved in intelligence work on the North West Frontier, undertaking missions in disguise and adding Persian to his knowledge of languages.
In 1917 he was moved to military intelligence at G.H.Q. Delhi and given responsibility for the Persian Gulf. The war in the Middle East was now entering a critical stage with the collapse of Russian forces following the October Revolution and the creation of a power vacuum in the Caucasus.
As 1918 dawned, a reinvigorated Turkish force, the Ottoman Army of Islam under Enver Pasha began advancing on Baku, much to the alarm of the British, who envisaged Enver's army crossing the Caspian, sweeping through Transcaspia (Russia's southernmost Central Asian possession) and on to India by way of Afghanistan.