Of the various censures imposed by the medieval Church the interdict has not recently received much attention. Apart from short articles in encyclopedias and dictionaries, and older works, there is nothing acceptable to the modern reader. Peter Clarke seeks to fill this gap. While the penalty of excommunication, the exclusion of the individual from the community and the sacraments of the Church, has been fully investigated in some excellent books, notably by Beth Vodola and Donald Logan, interdict has been neglected; this is perhaps because the notion of collective guilt and hence collective punishment has found favour often with tyrannical regimes and is thus generally repulsive, but that is not to say that it is any less important to investigate its theory and operation. The work of the late Stephan Kuttner and the Institute of Medieval Canon Law in identifying and establishing many of the texts of the medieval canonists opened up immensely valuable sources. Thus the views of the medieval canonists on interdict were waiting to be teased out and used by someone of patience and diligence, and Clarke may be said to weave his way through what Stephen of Tournai called the ‘silva ingens’ of the various decretals and interpretations of the law with an impressive assuredness. More problematical than the theory is the question of how, and how far, interdicts were implemented and enforced. Here the researcher is bound to rely upon the papal registers and on the comments of mainly clerical chroniclers. This study is not exhaustive on the imposition of interdicts throughout thirteenth-century Europe – nor does it claim to be. Considerable space is devoted to England. Clarke is heavily dependent on Cheney whose assumption that court business was not interrupted is questionable. A wider view of what an interdict meant for the community can be presented where there are surviving civic records and accounts of the proceedings of communes. Particularly rich are the records of the Italian commune of San Gimignano covering the episcopal interdict of 1289–93. Clarke devotes some pages to analysing this particular interdict and in less detail (because the records are not so extensive) interdicts on Dax and Béziers in south-west France. The account of how, at San Gimignano, the clergy stripped the altars, removing images and paintings which the commune considered to be their property, and of the hiring of ‘blackleg’ clergy who were prepared to provide spiritual comforts, gives some indication of how the laity responded. Stubbs's reflection that the interdict was the most ‘suicidal weapon’, denying the faithful the benefits of the sacraments of the medieval Church, highlights the dangers inherent in this sentence: the provision of an atmosphere in which heresies might flourish, the risk of growing anti-clericalism, and the discredit caused to the papacy when popes used the interdict for temporal purposes against secular rulers. Clarke's book is a measured analysis, particularly strong on the theory. It is likely to remain a standard work for some time.