Rear-Admiral Hugh Sinclair in a carriage in Tallinn
|Born||18 August 1873|
|Died||4 November 1939 (aged 66)|
|Service branch||Secret Intelligence Service (SIS/MI6)|
|Rank||Chief of the Secret Intelligence Service|
Admiral Sir Hugh Francis Paget Sinclair, KCB (18 August 1873 – 4 November 1939), known as Quex Sinclair, was a British intelligence officer. Between 1919 and 1921, After World War I, he was Director of British Naval Intelligence, and he helped to set up the Secret Intelligence Service (SIS, commonly MI6) before World War II.
Sinclair was educated at Stubbington House School and joined the Royal Navy at 13 in 1886 and entered the Naval Intelligence Division at the beginning of the First World War. He became Director of Naval Intelligence in February 1919 and Chief of the Submarine Service in 1921. He became the second director of SIS in 1923. He was promoted vice-admiral on 3 March 1926 and full admiral on 15 May 1930. 
Beginning in 1919 he attempted to absorb the counterintelligence service MI5 into the SIS to strengthen Britain's efforts against Bolshevism, an idea that was finally rejected in 1925. The SIS remained small and underfunded during the interwar years. By 1936, Sinclair realized that the Gestapo had penetrated several SIS stations and Claude Dansey, who had been removed from his station in Rome, set up Z organization, intended to work independently of the compromised SIS.
Sinclair was asked in December 1938 to prepare a dossier on Adolf Hitler, for the attention of Lord Halifax, the Foreign Secretary, and Neville Chamberlain, the Prime Minister. In the dossier, which was received poorly by Sir George Mounsey, the Foreign Office assistant undersecretary, who believed that it did not gel with Britain's policy of appeasement, Sinclair described Hitler as possessing the characteristics of "fanaticism, mysticism, ruthlessness, cunning, vanity, moods of exaltation and depression, fits of bitter and self-righteous resentment; and what can only be termed a streak of madness; but with it all there is a great tenacity of purpose, which has often been combined with extraordinary clarity of vision".
Sinclair became seriously ill with cancer, causing Alexander Cadogan to note on 19 October 1939, that he was "going downhill". On 29 October, Sinclair underwent an operation for his cancer and died on 4 November 1939, aged 66, five days before the Venlo incident.
- Christopher Andrew, "Sinclair, Sir Hugh Francis Paget (1873–1939)", rev. Oxford Dictionary of National Biography, Oxford University Press, 2004; online edn, May 2008
- "Senior Royal Navy Appointments" (PDF). Archived from the original (PDF) on 15 March 2012. Retrieved 6 September 2015.
- "No. 33139". The London Gazette. 5 March 1926. p. 1650.
- "No. 33606". The London Gazette. 16 May 1930. p. 3069.
- M. R. D. Foot, "Dansey, Sir Claude Edward Marjoribanks (1876–1947)", rev. Oxford Dictionary of National Biography, Oxford University Press, 2004; online edn, May 2008
- Michael Smith, Station X, Channel 4 Books, 1998. ISBN 0-330-41929-3, p. 20
- "Spy secrets failed to win Whitehall's trust". FT.com. 31 March 2005. Retrieved 1 Jul 2012.
- Foreign Office files Archived 2007-09-27 at the Wayback Machine
- Andrew. pp. 436–438.
| Director of Naval Intelligence
| Chief of the Submarine Service
Sir Mansfield Cumming
| Chief of the SIS