By 2011, when I retired from the Court of Appeal, I had spent eighteen years on the bench and before that twenty-eight years at the Bar. Over those years I had seen public law grow from a topic which was not even taught in law schools, except as a footnote to constitutional law, to a major area of legal practice and constitutional development. I had also had the luck to play a minor part in this metamorphosis. The offer, following my retirement, of a post as visiting professor of law in the University of Oxford provided the opportunity and the stimulus to confront the incuriosity I had met everywhere in my profession, as well as to satisfy my own curiosity, about how the public law of England and Wales (and in practice of Northern Ireland too) has come to be what it is. There was no way at my age to catch up on what should have been a lifetime’s research. Working on these essays, while it has been for me an education, has repeatedly reminded me how limited my knowledge is, for although practitioners in a common-law system sometimes have to deploy historical material, its use tends to be goal-oriented and to lack context. The book, accordingly, is primarily for judges, practitioners and students, though I hope that academic lawyers, legal historians and political scientists will also find things in it to think about. With the support of the Law Faculty, I delivered the twelve lectures which form the core of this book between 2012 and 2014. To them I have added two further papers delivered in the same period: one on the neglected public law of the Interregnum, initially delivered as the 2013 Sir Henry Hodge memorial lecture; the other, delivered in 2014 as the inaugural Rule of Law lecture for the Justice Institute of Guyana, on the influence of Dicey.