James Trenchard Hardyman was born in Madagascar in 1918. He was the son of Arnold Victor Hardyman and Laura Hardyman (ne Stubbs), who both worked as missionaries in Madagascar with the London Missionary Society from 1916-1938 and 1944-1950. As a child, James was sent to England to be educated under the guardianship of the Rev. and Mrs J. H. Haile. He became a missionary with the London Missionary Society in 1945. In the same year he married Marjorie Tucker.
From 1946-1974 they lived in Imerimandroso, Madagascar. In addition to his missionary work within the Antsihanaka area Hardyman became the Principal of the Imerimandroso College, training Malagasy pastors. Following his return to England, Hardyman worked as Honorary Archivist of the Council for World Mission at Livingstone House (1974-1991) and for the Conference of British Missionary Societies (1976-1988). In this capacity he oversaw the deposit of both archives at the School of Oriental and African Studies. From 1974-1983 he also worked for the Overseas Book Service of Feed the Minds.
At the age of eleven, Hardyman was given a second-hand copy of a book on Madagascar by Haile. The book, published anonymously in the 1840s, began his collection of published and unpublished material relating to Madagascar, which was to become the largest personal collection on Madagascar in existence. Hardyman used much of the material in his thesis, for which St. Edmund's Hall, Oxford, awarded him a B.D. in 1952. He continued to collect information on the subject throughout his life. James Trenchard Hardyman died on 1 October 1995.