Colin was the only son of Rice Mansel Dillwyn [his original surname was Nicholl but he assumed that of his mother], a mining engineer, and his wife Harriet Florence Gilbertson, of Bridgend, Glamorgan. They had four daughters.

He was educated at Marlborough and the Queen’s College, Oxford and was appointed a Lecturer in Modern History at Christ Church in 1936. Earlier that year, he had left Dover on 8 February for Costa Rica on the Columbia. He gave his address as 17 Montagu Street, W.C. and his employment as Fellow of Queen’s College, Oxford. He arrived back at Plymouth on 3 August from Barbados on the Crijnssen. In 1938, he visited the United States, leaving Southampton on 12 March and returning there on the Europa from New York on 20 April.

Whilst at Marlborough he had been a Cadet Lance Corporal in the OTC. He was gazetted Second Lieutenant on 4 July 1939 in the 4th Battalion Oxford and Buckinghamshire Light Infantry.

His obituary stated “early in the morning whilst leading his men in an attack near Hondschoote, Belgium, dearly loved son of R.M. Dillwyn”.

He is buried in Oye-Plage Communal Cemetery. Plot Row 3. Grave 19.

See Glamorgan archives GB 0214 DDJ for information about the Dillwyn family.