Book excerpt: This volume provides an introduction to the United Kingdom's constitution that recognises and embraces its historical, social, political, and legal dimensions. It critically examines the radical changes to the UK constitution that have occurred over the last thirty years, paying particular attention to the revival of the constituent territories of the UK - Wales, Scotland, Northern Ireland, and England - and to the increasing role played by the judges in constitutional disputes. The UK constitution is presented as being shaped by a set of constitutional principles, including state sovereignty, separation of powers, democracy, subsidiarity, and the rule of law, principles which set the overall structure of the constitution and inform statutes and the decisions of judges. Adopting a principled approach to the UK constitution allows us to see both the clarity of the constitution's structure and also helps explain its complexities.