Book excerpt: This book radically reassesses the reform of the Irish Church in the twelfth century, on its own terms and in the context of the English Invasion that it helped precipitate. Professor Ó Corráin sets these profound changes in the context of the pre-Reform Irish church, in which he is a foremost expert. He re-examines how Canterbury's political machinations drew its archbishops into Irish affairs, offering Irish kings and bishops unsought advice, as if they had some responsibility for the Irish church: the author exposes their knowledge as limited and their concerns not disinterested. The Irish Church, its Reform and the English Invasion considers the success of the major reforming synods in giving Ireland a new diocesan structure, but equally how they failed to impose marriage reform and clerical celibacy, a failure mirrored elsewhere.