Educated at Queen's College, Oxford, he began his career as a meteorologist. Although an Englishman by birth, he developed a lifelong interest in the history and genealogy of the royal families and nobility of mediaeval Wales. He learned to read the Welsh language and went on to publish a compendious series of volumes containing the edited texts of medieval Welsh genealogical tracts and his own detailed reconstructions of family lines. His work is now an essential resource for any serious student of early and medieval Welsh history.
Much of his work has been made available online.