The planning systems of Britain and continental Europe have been constructed in very different ways and make different assumptions about the way in which the decisions about the management of place and space shall be made. That the differences are due to differences in the legal systems is understood in a general way. What is perhaps less well understood is how profound the impact of legal thinking on planning has been. This impact is not just about the minutiae of legal draughtsmanship or the detailed consequences of jurisprudence; legal theory and practice have shaped fundamentally the way in which planning problems are conceptualised and solved. This book presents the origins of common law in the British Isles and the reasons for its gradual separation from the legal tradition of continental Europe from which it was born. It explores the differences between the British common-law tradition and those countries whose legal systems derive from it such as the United States and Australia, and the code based systems of continental Europe. Arguing that the common-law tradition has been critical in conceptualising key planning terms such as 'amenity', 'development' and above all 'reasonableness', in establishing the quasi-judicial approach to public administration in the field of planning, and in defining property rights to include those of future owners, Phillip Booth demonstates that the influence of the legal system on planning has been much greater than previously understood.