AbstractThe Medieval English state had been studied by historians largely on its own terms and from its own records, enriched by an occasional reference to continental comparisons and contrasts. This will no doubt remain the primary approach; but it can be usefully supplemented by also looking at the English state through its impact on other ‘Celtic’ countries in the rest of Britain and Ireland which it brought, either permanently or temporarily, within the ambit of its power. English rule in Wales, Ireland and, briefly, Scotland can thereby serve as a mirror in which one may see refracted some of the essential qualities andmentalitésof the English state itself—notably its increasingly self‐consiously English character in terms of its own identity and institutions and the growing assumption that there should be a good measure of governmental uniformity and bureaucratic answerability in the lands which it had annexed. English rule in the ‘Celtic’ countries also brings into sharp focus how dependent the medieval English state was for its operation on an effective relationship between state and society; the failure to replicate that relationship substantially in Wales and Ireland showed that there was more to successful political integration than military might and governmenta