The main part of this volume, and the only part not to have appeared in print before, comprises the Cook Lectures which I delivered at the Law School of the University of Michigan at Ann Arbor in April 1990. I wish to express my profound appreciation and gratitude both for the honour of the invitation and the most friendly entertainment I received. Special thanks go to the dean, Professor Lee Bollinger, who invited me, and to old friends (more particularly Tom Green) who looked after me. I owe very special thanks to Lillian Fritzler, the dean's secretary, who went to so much trouble over me, and to Susan Kybett who made the whole thing possible by ferrying the lecturer's decaying carcase from place to place. I include here also the two inaugural lectures I delivered in the University of Cambridge on 15 February 1968 and 26 January 1984 when moving into two successive chairs of history, partly because they help to provide a little more body for the volume, but mainly to contain reflections on the reality of the labours in which I have spent nearly half a century of my professional life. But having got all this off my chest I rather hope that it is still too early to sing Nunc dimittts.