H.L.A. Hart was the pre-eminent legal philosopher of the twentieth century. As a scholar he single-handedly reinvented the philosophy of law and revolutionized our understanding of law as a social institution. Hart's approach to legal philosophy was at once disarmingly simple and breathtakingly ambitious, combining the insights of the Utilitarian tradition and the new linguistic philosophy of J.L. Austin and Ludwig Wittgenstein. He sought to elucidate a concept of law that would be of relevance to all forms of law, wherever or whenever they arose. This book is both an intellectual and a psychological biography, following his life from modest origins as the son of Jewish tailor parents in Yorkshire to worldwide fame as the most influential English-speaking legal theorist of the post-War era. It traces his successive metamorphoses; from Yorkshire schoolboy to Oxford scholar, successful barrister, intelligence officer, philosopher, and, finally, Professor of Jurisprudence at Oxford. Nicola Lacey draws upon Hart's previously unpublished diaries and letters to reveal a complex interior life. Outwardly successful, Hart was in fact tormented by doubts about his intellectual abilities, his sexual identity and his capacity to form close relationships. Her biography also sheds fascinating light on the origins of his ideas, and assesses his overall contribution to the philosophy of law. Above all, it is a chronicle of a life which made an impact far greater than many of us realize.