Historians are still striving to understand the extraordinary richness and complexity of the religious ideas of the Gregorian Reform. In this powerful and insightful study Louis Hamilton highlights the significance of the dedication of churches during the reform movement, both for the promotion of papal authority and as a metaphor in reforming polemic for the renewal and restructuring of the Church and Christian society. Using a wide variety of especially liturgical and hagiographical sources, he shows how central this theme was to the religious ideas of the reformers. Dedications themselves were great ceremonial and public occasions, and from the late eleventh century onwards popes, notably Urban ii and Paschal ii, became increasingly active in performing such dedications themselves, especially in southern Italy, where they spent a lot of their time, and on their visits to France: Urban in 1095–6 and Paschal in 1106–7. By doing so they were very publicly stressing their role as the supreme authority within the Church, but Hamilton demonstrates that they were also putting into practice a motif that had informed the thought of some of the key intellectual leaders of the reform, notably Peter Damian, the canonist Anselm of Lucca and Bruno of Segni, to each of whose development of this theme Hamilton devotes a chapter of his book. In doing so he also reminds us how central the liturgy was to the reform movement, and that liturgy and ritual were not simply a constant element in the background, but rather a dynamic and changing force at the centre of the reforming ideal. At a practical level dedications played an important social function, sometimes resolving internal disputes in Italian towns, as at Bari in 1089 and Parma in 1095, and also provoking outbursts of religiosity and manifestations of the miraculous – as well as, or so the reformers hoped, encouraging Christians to reflect on the renewal and sincerity of their faith. At a more rarefied level sermons and tracts aimed at the clergy used discussions of dedication and the metaphor of church architecture as an allegory for the Church as a community of all Christians to promote papal authority. Hamilton paints a convincing, and lucidly presented, picture – explaining his terms clearly and avoiding jargon – although the fashionable emphasis on ‘sacred space’ occasionally grates. The extended discussion of the De laudibus of Bruno of Segni, though interesting in itself, is not as convincingly tied to the overall argument as the rest of the book; but by contrast his perceptive discussion of Bruno's later tract, De sacramentis, which Hamilton argues clearly postdates the crisis of 1111–12, shows how Bruno's alienation from Paschal ii after the latter's surrender to the Emperor Henry v and his own deposition as abbot of Montecassino led him to tone down earlier emphasis on papal authority and stress rather the episcopal role in ecclesiastical dedication. There is, however, one element on which the author might have laid more weight than he does. He tends to assume that the growing number of papal dedications of churches was part of a conscious assertion of papal authority; that, for example, the dedication of St Nicholas, Bari, in 1089 served, inter alia, to stress Urban ii's legitimacy as pope at a time when much of Rome was still in the hands of supporters of his imperialist rival Clement iii. Yet Urban himself, in the bull which he granted to that church to mark its dedication (to which the author does not refer), said expressly that it was ‘against Roman and Apostolic custom’ to perform such a personal consecration, but that he was making an exception both out of reverence for St Nicholas and because of the insistent request of the people of Bari. Similarly, at the dedication of the abbey church of Holy Trinity, Cava, in 1092, discussed at some length by Hamilton, the monks themselves were keen for their church to receive such a distinction since it confirmed their claims to be exempt from the authority of the archbishop of Salerno. The growing number of papal consecrations after 1088 was also a response to pressure from below, and not just an element in the increasing assertion of papal authority. Nevertheless, notwithstanding these mild criticisms, one can wholeheartedly recommend Hamilton's excellent book as an original, thoughtful and thought-provoking addition to the literature on the Gregorian Reform.