Crofton Arbuthnot was born in Natal, South Africa, on 4 September 1901, the son of Crofton Arbuthnot and Mrs Arbuthnot (née Maby).  He was the brother of Doreen, Eugenie, Joan, Donald and John Arbuthnot. He joined the Royal Navy as a Colonial Cadet on 15 May 1915 and trained at the Royal Naval College, Dartmouth.

In December 1918 Midshipman Crofton Arbuthnot (Seniority 15 September 1917) was serving in the battleship HMS COLLINGWOOD to which he had been appointed on 26 September 1917. He also served in the battleship HMS MALAYA. He was promoted Sub Lieutenant in 1921 and served in the cruiser HMS LOWESTOFT, which was the flagship at the Cape of Good Hope, and then in HMS BIRMINGHAM. He was promoted Lieutenant on 15 September 1923 and served in the battleship HMS RAMILLIES.

In August 1927 he was serving in the Patrol Boat PC74 ‘Second in Command’ to which he had been appointed on 28 March 1927. He then served as the First Lieutenant of the destroyer HMS TETRARCH in the Atlantic Fleet. He is still listed as a Lieutenant in the July 1931 Navy List but no appointment was noted. He was promoted Lieutenant Commander on 15 September 1931.

He was appointed as the Executive Officer of the Submarine Depot Ship HMS ADAMANT in November 1931 which had been, temporarily, attached to the Sixth Submarine Flotilla, Portland, for the Atlantic Fleet Spring Cruise. HMS M2 was lost with all hands in an accident in the Channel on 26 January 1932. It is believed that the submarine had surfaced to fly off its Parnell Peto seaplane when it was flooded through the open hangar door and access hatch.

Crofton Arbuthnot, who was unmarried, was not a qualified submariner but may have been onboard the submarine as an observer/passenger.