The future of the United Kingdom is an increasingly vexed question. This book traces the roots of the issue to the Middle Ages, when English power and control came to extend to most of the British Isles. By 1300 it looked as if Edward I was in control of virtually the whole of the BritishIsles. Ireland, Scotland, and Wales had, in different degrees, been subjugated to his authority; contemporaries were even comparing him with King Arthur. This was the culmination of a remarkable English advance into the outer zones of the British Isles in the twelfth and thirteenth centuries.What remained to be seen was how stable (especially in Scotland and Ireland) was this English 'empire'; how far the northern and western parts of the British Isles could be absorbed into an English-centred polity and society; and to what extent did the early and self-confident development of Englishidentity determine the relationships between England and the rest of the British Isles. The answers to those questions would be shaped by the past of the country that was England; the answers would also cast their shadow over the future of the British Isles for centuries to come.