As a conscientious objector in World War II, he was directed to work on the land – firstly as a forestry worker in the Afan Valley, then from September 1941 in market gardening in a Cardiff Quaker community.
[3] After a short time working as a graphic designer for the advertising agency J. Walter Thompson in London, Elwyn moved to Portsmouth, where he taught at the College of Art.
His numerous contributions to the annual Pictures for Welsh Schools exhibitions, staged by the Society of Education through Art, which were shown at the National Museum of Wales, Cardiff, between 1950 and 1968.
Memory and imagination are the source of his evocative recreations of the Cardiganshire landscape, with secluded villages, lonely farms, cottages, barns and sweeping country lanes receding in sharp perspective towards the horizon.
The latter year marked his 80th birthday, for which Aberystwyth University's Robert Meyrick researched and curated a major retrospective of his work for the National Library of Wales.
He drew continually on his wide experience of the working life of the countryside, the bustling farmyards and cattle pastures of the Teifi and Ceri valleys, and the upland rural areas.
In 2000, the National Library of Wales staged a Memorial Exhibition to coincide with the Scolar Press publication of Robert Meyrick's monograph on John Elwyn.