After graduation, he took a post as a lecturer at the University of Sheffield (1965–69), and then later at the University of Manchester (1970–73). He became a Fellow and Tutor in Modern History at Balliol College in 1973. In 1990, he took a post at the University of Chicago as Professor of History, where he became chair of the History Department in 1992 and Dean of the Division of Social Sciences in 1993. He returned to Oxford in 1994 to become Master of Balliol College (1994–2000).