adapted from Wikipedia:
Sir Basil Thomson (1861–1939) was a British intelligence officer, police officer, prison governor, colonial administrator, and writer.
After studying at Eton and Oxford (a university career cut short by depression) he secured a cadet position at the Colonial Office, where he assisted the Governor of Fiji from 1884, but was then invalided back to England after contracting malaria. He returned to Fiji after his marriage, and then on to Tonga.
Back in Britain, he was admitted to the bar in 1896. Instead of becoming a barrister, Thomson accepted the position of deputy governor at HM Prison Liverpool, then as governor of Northampton, Cardiff, Dartmoor, and Wormwood Scrubs prisons.
In June 1913, Thomson was appointed Assistant Commissioner "C" (Crime) of London's Metropolitan Police, which made him the head of the Criminal Investigation Department (CID) at New Scotland Yard. When World War I broke out in 1914, the CID found itself acting as the enforcement arm for Britain's military intelligence apparatus: while the newly formed Secret Service Bureau (later known as MI6, the Secret Intelligence Service), and the intelligence arms of the War Office and the Admiralty, collected intelligence on suspected spies in Britain, they had no arrest powers.
One who he interrogated was ‘Mata Hari’, the Dutch exotic dancer later to be executed by the French as a spy. In 1916 she was taken off a ship sailing from Spain to the Netherlands at Falmouth as a suspicious person and brought to London where she was interrogated at length by Thomson. He refers to this in his book Queer People.
In 1919, while remaining Assistant Commissioner (Crime), he was appointed Director of Intelligence at the Home Office, in overall charge of every intelligence agency in the country, but in 1921 he fell out with Lloyd George and was asked to resign. The reasons for this remain mysterious.
He started writing in 1894, beginning with a book about his experiences in Fiji, South Sea Yarns. His book, Queer People (1922), covers his time at the CID and during the First World War.