In 1980, he was appointed lecturer at the University of Manchester Institute of Science and Technology (UMIST). In 1983, he was appointed lecturer and then reader in theoretical chemistry at the University of Cambridge, where he was fellow and senior tutor of Magdalene College. In 1996, he was made director of the Centre for Theoretical and Computational Chemistry and professor at University College London. In 2002, he moved to the University of Oxford, where he was head of the Division of Mathematical and Physical Sciences and professorial fellow of St John's College. He was elected President of Magdalen College, Oxford in 2005.
