Harry Hamilton Marshall was born in Brighton in Sussex on 7 December 1906, the son of Major Ernest Theodore Marshall. He joined the Royal Navy as a Cadet on at the age of thirteen in 1919. He was promoted to Midshipman (E) on 15 January 1925 and was appointed to the Engineering Course at the Royal Naval Engineering College at Keyham. He was promoted to Acting Sub Lieutenant (E) on 1 May 1927 and confirmed Sub Lieutenant (E) on 16 January 1928. He was appointed to the cruiser HMS VINDICTIVE on 30 April 1928. Harry Marshall was promoted to Lieutenant (E) on 16 August 1929.

He was appointed to HMS CYCLOPS in the Mediterranean ‘for Submarines‘ on 27 April 1931 and to HMS OXLEY as the Engineer in December 1931. An appointment to HMS DOLPHIN ‘for duty with Submarines‘ followed on 10 September 1934.

Harry Marshall died on 10 June 1935, by suicide from self-inflicted wounds, at home in Beckenham, Kent. He was the husband of Lilian Janet Marshall.