[2] He studied history at St John's College, Cambridge and was a member of the Lady Margaret Boat Club.
[1] On 14 February 1949, as part of National Service, he was granted an emergency commission in the Royal Regiment of Artillery with the rank of second lieutenant.
[2] On 21 December 1951, he was transferred to the Supplementary Reserve officers and granted seniority in the rank of second lieutenant from 4 August 1950.
[2] While his main duties at the academy were to teach the officer cadets military history, he also coached the Boat Club.
[2] In 1963, Halladay coached a team from the Royal Military Academy Sandhurst to win the Ladies' Challenge Plate.