I completed my undergraduate degree in Zoology (1966) and my DPhil (1970) at Pembroke College Oxford. After a year as a Departmental Demonstrator in Ornithology at Oxford I moved to the University of British Columbia as an Assistant Professor of Ecology (1970-73). I then spent a period at the University College of North Wales in Bangor as lecturer in Zoology (1973-75) before returning to Oxford as University Lecturer in Zoology in the Edward Grey Institute of Field Ornithology. I was a Fellow of Wolfson College until 1981, when I became EP Abraham Fellow of Pembroke College. Between 1988 and 2005 I was a Royal Society Research Professor at Oxford. From 1994 to 1999 I was Chief Executive of the Natural Environment Research Council and between 2000 and 2005 I was Chairman of the UK Food Standards Agency. In 2005 I gave the Royal Institution Christmas Lectures.

In 2007 I chaired a working party of the Nuffield Council on Bioethics to produce a report on the Ethics of Public Health. I sit in the House of Lords as an independent cross-bencher and I am Chairman of the House of Lords Science and Technology Select Committee. I am also a Trustee of the Nuffield Foundation, Chairman of the UK Science and Technology Honours Committee and Chairman of the Royal Society's Science Policy Advisory Group. I sit on the UK Climate Change Committee and chair its Adaptation Sub-Committee.