Career
Somerville joined the Royal Navy as a cadet in 1877. He trained as a Hydrographic Surveyor, was promoted to Commander on 31 December 1901, Captain in 1912 and Vice Admiral on 1 August 1919. He retired on 2 August 1919.
While on surveying duties in the Western Pacific, Somerville built a significant collection of ethnographic artifacts from the Solomon Islands - now in Pitt Rivers Museum, Oxford.
In 1908, while surveying in British waters, he read a book suggesting stone circles and standing stones might have astronomical significance. He thereafter devoted much of his time to surveying such monuments in Britain, Ireland and elsewhere, and became a recognised expert in the field of archaeoastronomy.
He contributed papers to the Antiquarian magazine. As part of the late summer 1917 reorganisation of the burgeoning British Secret Intelligence Service, led by Mansfield Smith-Cumming and his de facto deputy, Colonel Freddie Browning, Somerville was appointed as "officer in charge of the Naval Section within the Secret Service Bureau." This was the first career naval officer posting to the Secret Service.
In February 1919, Somerville wrote a review setting out a number of basic principles for service and encouraging the development of specialist intelligence technical skills within the navy for intelligence gathering and analysis.
After his retirement he returned to the family home at Castletownshend, near Cork in Ireland. On 24 March 1936 he was murdered when four men burst into the house and fired a revolver. Ireland Republican Army chief of staff Tom Barry was involved in the shooting.
The Vice-Admiral was targeted for recruiting local men to join the Royal Navy.
He was the younger brother of the novelist and artist, Edith Somerville, who finished his biography of William Mariner for its posthumous publication.