Offering a new interpretation of the sermon ‘De ordinatione beati Gregorii anglorum apostoli’, a text preserved in Eadmer's ‘personal manuscript’ (Corpus Christi College, Cambridge, MS 371), this article argues that the cult of St Gregory the Great was promoted by Archbishop Lanfranc (1070–89) and Archbishop Anselm (1093–1109) in order to undermine the pretensions to apostolic rank of St Augustine's Abbey, Canterbury. It draws attention to the existence of a hitherto unrecognised but major conflict over apostolic authority that took place in England after the Norman Conquest; a conflict that involved the king as well as Canterbury's most important churchmen. In so doing, this essay contributes, more generally, to our understanding of the roles that the cult of saints and its rhetorical structures played in battles over status and rank order.