James Douglas Charlton Edgar was born in Brantford, Ontario, Canada, on 22 May 1903, the son of Minnie Ott and her husband, James Douglas Edgar, a Presbyterian minister. He lived in Toronto before moving to Edinburgh. There he attended the Edinburgh College of Art from 1924 to 1928, graduating with a diploma in painting. The college was conservative with an emphasis on sound drawing. The course was primarily intended for teachers, and Edgar's other studies – he graduated MA in history (1927) and DipEd (1929) from Edinburgh University – confirm the impression he was training for such a career. In 1924 he met John Weeks, who had previously been in New Zealand and was later an influential teacher in Auckland; the two became good friends.
On 10 February 1931 at Edinburgh, Edgar married Mona Marguerite Barnetson. After teaching briefly in Scotland, he and Mona emigrated to Dunedin, New Zealand, in 1931 to the Dunedin School of Art at King Edward Technical College. The school had been revitalised since 1925 under R. N. Field and W. H. Allen, but Allen resigned in 1930 and Edgar replaced him as painting instructor. He acknowledged that Field and Allen had fostered originality, but felt the students followed them too blindly and that standards of execution and thoroughness were low. He and his fellow instructor, Gordon Tovey, helped to change this.
The new arrivals were not wholly congenial to Field, who took leave from 1933 to 1935, nor did he much care for the regime they imposed when Tovey was made director in 1936. Even so, the school continued to attract and succour good students, among them Toss Woollaston, Doris Lusk, Anne Hamblett, Colin McCahon and Patrick Hayman. Lusk in particular valued Edgar's teaching and his enthusiasm for landscape. He painted a kind of mild, late impressionism in oils and watercolours. He was a printmaker and occasional collagist and was particularly inspired by Central Otago. His 'Clear morning, autumn on the Kawarau' (1937) is characteristic, while 'The green hat', about the same date, shows he could be more progressive when inspired. In these years, J. D. Charlton Edgar, as he was always known, sat on the council of the Dunedin Public Art Gallery, where tension existed between detractors and champions of the local avant-garde.
In 1938 and 1939 the Edgars went on leave to America and Europe, and to Scotland where Edgar completed his BEd. Back in Dunedin he became head of the school in 1941, staying until the end of 1942. In these war years he served in a camouflage unit and in 1943 became head of the art department of the Auckland Training College. He remained till 1963, having taught and influenced notable artists including Stanley Palmer, Para Matchitt and Ralph Hotere. His wife's death in 1961 affected him greatly, perhaps the more so because they had no children. It led to his gift in her name of a collection of modern New Zealand works to the Hocken Library, which helped transform that institution.
In 1965 Edgar became director of the Dunedin Public Art Gallery. While continuing to collect the old and the foreign he accelerated the acquisition of paintings by Frances Hodgkins and contemporary New Zealand and Australian works, and instituted a programme of solo exhibitions by living New Zealand artists. Among these Edgar saluted Field and Allen as the instigators of modernism in New Zealand.
He also established a new position of assistant director, to which James Mack was appointed in 1968. Taking offence at Mack's homosexuality, Edgar influenced the gallery council not to renew his contract when it expired in 1971. He thus alienated Rodney Kennedy and Charles Brasch, powerful patrons, and with them the more progressive element in New Zealand's art world. The gallery was damaged. After Edgar's own retirement in 1971 he was a rather isolated and forlorn figure until his death on 12 October 1976. The survey exhibition and MBE accorded him the same year can have been little consolation.
As an artist Edgar was a minor though prolific practitioner, perhaps most significant for focusing some attention on Central Otago. His impact on the collecting policies of both the Hocken Library and the Dunedin Public Art Gallery was considerable and progressive, if not always very discriminating. He made his greatest contribution as a teacher and administrator. No artistic visionary, he nevertheless bridged the gap between those who were and their employers. While he was able to do this he helped institutions flourish in an essentially hostile environment. When he lost the knack, the scale of the resulting breakdown was one measure of his achievement.