He served on the Western Front in France from 1916 to 1917, but was then invalided home and worked for the remainder of the war at the British Ministry of Information.
[3] In 1948 Gwynn returned to Ireland and took up the post of research professor of Modern Irish History at University College Cork.
[4][2] Alice's paternal grandfather was Edward Livingston Trudeau (1848–1915) an American physician and public health pioneer who helped to establish principles for disease prevention and control, particularly for tuberculosis.
[5] Denis Gwynn died at his home in Malahide Dublin, on 10 January 1973 and was buried at Stamullen Cemetery Co Meath.
[6] The novelist Jessie Victor Rickard lived the final years of her life, until her death in 1963, at Denis Gwynn's house in Montenotte, Cork.