There have been few studies of the Law Lords, and no study of them by a political scientist for more than ten years. This book concentrates on the arguments the Law Lords use in justifying their decisions, and is concerned as much with the legal methodology as with the substance of their decisions. Very close attention is paid to the different approaches and styles of judicial argument, but the book is not restricted to this traditional analytic approach. One chapter applies the statistical techniques Americans call 'jurimetrics' and have successfully used on the US Supreme Court. The main theme is that the Law Lords enjoy and fully utilise far more discretion in their judgements than is normally admitted, and that much depends on exactly which judges happen to hear a case. the second part of the book shows the impact this extreme discretion has had in shaping both public law and areas of civil law.