Methodist historian, born at Bishop Auckland. He was educated at Kingswood School, Magdalen College, Oxford and Fitzwilliam College and Wesley House, Cambridge, where he gained first class honours in Church History. This was followed by a research year at Tübingen University. He was President's Assistant at Didsbury College 1963-1964 and from 1965 to 1970 was a tutor at Hartley Victoria College. From 1970 until his retirement in 1994, he was lecturer and later Bishop Fraser Senior Lecturer in ecclesiastical history at Manchester University. His study of The Future of John Wesley's Methodism was published in 1965. In 1977 he gave the Wesley Historical Society's annual lecture on 'Wesleyanism and "the world" in the later nineteenth century'. And in 2004 his Peake Memorial Lecture was on 'A.S. Peake and the centenary of the founding of the Faculty of Theology, Manchester'. His definitive Reasonable Enthusiast: John Wesley and the Rise of Methodism (1989; 3rd edition, 2002) remains the leading scholarly biography of Wesley. Perfecting Perfection: Essays in honour of Henry Denman Rack was published in 2015.