Samuel Horsley was the son of a lecturer at St Martin-in-the-Fields and the grandson of a principal of Edinburgh University. He was a student at Trinity Hall, Cambridge, and a tutor at Christ Church, Oxford. An enthusiastic Greek scholar, he took pleasure in discussing a range of authors, especially Thucydides, with his son. He was a fellow of the Royal Society and a keen student of mathematics. From 1779 to 1785 he edited the works of Sir Isaac Newton, although it was later alleged that he overlooked, possibly destroyed, a ‘cart-load’ of papers on religious subjects which showed Newton to be Unitarian in faith. Horsley, a great trinitarian champion, probably regarded these as unfit for publication. He became Archdeacon of St Albans in 1781 and a prebendary of Gloucester in 1787. Horsley was an enthusiastic supporter of Pitt the Younger, to whom he owed his elevation to the episcopate in 1788 as Bishop of St David's. He spoke and voted for the government in the House of Lords and strongly supported Pitt's war effort and the need to finance it. He enjoyed some modest preferment, becoming Bishop of Rochester in 1793 and of St Asaph in 1802. He combined a staunch conservatism in both social and political concepts, with a genuine Christian faith and concern for the well-being of the church. He was perceptive enough to be aware of the exigencies of the changing situation and to make the necessary adjustments in the general tenor of his argument.