Admiral Sir Hugh Sinclair (1873-November 4, 1939), nicknamed 'Quex', was the Director of British Naval Intelligence during the First World War and helped to set up the Secret Intelligence Service (SIS) before the Second World War.

He joined the Royal Navy in 1883 and entered the Naval Intelligence Division at the beginning of the First World War. He became Director of the Division in February 1919, and later head of the Submarine Service. He became the second director, or 'C', of the British Special Intelligence Service in 1923.

Beginning in 1919 he attempted to absorb the counter-intelligence service MI5 into the Special Intelligence Service (SIS) to strengthen Britain's efforts against Bolshevism. When this idea was finally rejected in 1925, he set up his own Counter-Espionage (CE) section. In 1935 he set up the Z Organization, a section of SIS operating in Europe, intended to carry on working independently should SIS itself become compromised. In 1938, with a second war looming, Sinclair set up Section D, dedicated to sabotage. In the same year, using his own money, he set up the Government Code and Cypher School at Bletchley Park.

References

"Institutionalising Intelligence", Philip HJ Davies, University of Reading (http://www.psa.ac.uk/cps/1994/davi.pdf)