1. Professor of Law, King's College London and Honorary Professor in Law, University of Sheffield. This is a revised version of the IMLAB Public Lecture 2004 given at the University of Liverpool on 14 January 2004. An earlier version of the article was presented to the Institute of Professional Ethics at the University of Keele in November 2003, and a subsequent version to the Cambridge Bioethics Forum, at Clare College, Cambridge, in April 2004. I am grateful to all who participated at those...