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Administrative / biographical background
Sinclair was born on 18 August 1873, and joined the Navy in 1886 aged 13. During his early career he specialised in torpedo work and received excellent commendations. During the First World War, Sinclair served as assistant director of the mobilization division of the Admiralty war staff (1914-1916), commanded HMS RENOWN (1916-1917) and was Chief of staff of the Battle Cruiser Force (1917-1919). From 1919 to 1921 Sinclair was director of naval intelligence - his first major involvement in this area. In 1919 he was given the task of founding the new signals intelligence agency - the Government Code and Sipher School (GC & CS). Sinclair was promoted to Real-Admiral in 1920, and undertook a tour of duty as Chief of the Submarine Service from 1921 to 1923. At this point he was appointed Chief of the Secret Service - the operational head of the Secret Intelligence Service (SIS). He was additionally, the non-operational director of the GC & CS. Sinclair received the promotion to Vice-Admiral in 1929. The SIS at this time was a small, under-funded foreign intelligence agency, staffed mostly by men with a service history. The main priority of the SIS until 1933 was gathering intelligence from Soviet Russia. However, the rise of Adolf Hitler meant that Germany, Italy and Japan became the priorities during the 1930s. In 1930 Sinclair was promoted to Admiral (retired) and was appointed the KCB (Knight Commander of the Bath) in 1935. He held a great deal of influence in Whitehall during and after this time, including with the Prime Minister Neville Chamberlain. On 4 November 1939, Sinclair died in London.