Legal writer, antiquary and member of the Royal Irish Academy. He was educated at Trinity College, Dublin, where he struck up a lifelong friendship with Thomas Moore (1779–1852; DNB). He was called to the Irish Bar in 1800, but never practised, instead holding posts as examiner to the prerogative courts and as Assistant, later Chief, Librarian of the King’s Inns, Dublin. His charitable and educational activities were numerous and included playing an important part in the Society for Promoting the Education of the Poor in Ireland. In 1818 Mason founded the Irish Society for ‘promoting the scriptural education and religious instruction of the Irish-speaking population chiefly through the medium of their own language’ and he was also the moving force behind an association for the improvement of Irish prisons and prison discipline. His best-known publication was a concise account of the history of Irish common and statute law from the Anglo-Norman invasion to the reign of Charles I – Essay on the Antiquity and Constitution of Parliaments in Ireland (1820). Mason met Southey in Keswick in autumn 1812. They corresponded for some twenty years, though few of their letters survive. Mason was especially keen to solicit Southey’s support for his educational projects.