This handsome volume presents over forty episcopal letters, many translated into English for the first time, from the twilight years of the eastern Roman Empire. Neil and Allen are to be commended for having marshalled the material so carefully, and for their lucid introductions to each tranche of correspondence. The letters all date from between ad 500 and 700, and have been organised into three broad categories: first, those dealing with the conclusion to the Acacian schism (negotiated by Hormisdas of Rome in 519); secondly, letters detailing conflicts within the anti-Chalcedonian Churches in Syria and Egypt during the sixth century; thirdly, letters from a range of participants in the monoenergist and monothelite controversies in the seventh century. As Neil and Allen rightly note, these sources offer a valuable window onto the ways in which ecclesial disagreements were variously provoked or soothed, claims to episcopal authority were expressed or challenged, and rhetorical strategies of persuasion or threat were deployed (especially between Rome and Constantinople). The letters also allow for some sophisticated analysis of episcopal networks of communication and support (building, for instance, on Adam Schor's work in Theodoret's people, Berkeley–Los Angeles 2011). There are, admittedly, some significant limits to what the letters can reveal. Their episcopal authors would have conveyed some (often the most sensitive) instructions or opinions personally through the letter carrier, rather than committing them to the written record. Also, the collections in which the letters have been preserved (for instance, the Collectio Avellana in the case of Hormisdas's correspondence) are themselves particular selections shaped by later political and ecclesiastical agendas. None the less, there are all sorts of fascinating details to uncover here. The anti-Chalcedonian material is especially compelling, since it reveals, warts and all, how these Churches (often portrayed as a monolithic miaphysite bloc) were themselves riven by all sorts of doctrinal disagreements: the corruptibility or incorruptibility of Christ's body, whether Jesus was ignorant in some earthly matters (for Jesus asks of Lazarus, ‘Where have you laid him?’), and the spectre of tritheism in delineating the hypostatic distinctions in the Godhead. Even more importantly, the Council of Chalcedon (451) casts its long and dark shadow across almost all the letters in Neil and Allen's book. It is remarkable how many parties choose to establish their orthodox credentials by narrating distinct conciliar genealogies, tracing the golden thread of pure doctrine through a particular selection of councils. Some bishops include Chalcedon in their narratives (whether proudly or begrudgingly), others (quietly, or loudly) omit it – but earlier councils too (especially the Council of Ephesus of 431) are also part of a still-malleable tradition. Neil and Allen are, understandably, keen to foreground the political context of the letters, but their claim that ‘most major religious controversies between 500 and 700 ce can be explained by external or internal political circumstances’ (p. 26) perhaps pushes the point a little too far. Assuredly, the theological is often political, but the relationship works in both directions. Again and again, the authors of these letters seek to understand political conflicts and divisions in explicitly theological terms. Indeed, one of the under-explored aspects of the letters is the amount of scriptural exegesis and interpretation, conducted with a seriousness and urgency that belies the view that it is mere background noise to the bishops’ real, and essentially ‘political’ concerns. Nevertheless, Conflict and negotiation in the Early Church makes a valuable contribution to the study of this period, and, in opening up such rich sources to a wider readership, has performed a very great service.