The chapter compares different uses of the legend of Troy as a ‘Trojan preface’ to historical and literary texts in medieval England, Wales, and Ireland. Typically used to introduce narratives of nationalist significance, the ‘Trojan preface’ forms a distinctive genre that functioned to establish or confirm myths of national origin. The work of early historians such as Henry of Huntingdon and Geoffrey of Monmouth provides examples of the uses of Troy to construct a particular kind of English identity. In Welsh and Irish texts, the Trojan legend was inserted as a chronological milestone which aligned the ethnic histories of Wales (or Britain) and Ireland with world events. The legacy of Rome was another source of English identity which worked to exclude the early British people and their descendants, the Welsh. Rome was also an important point of reference for the Welsh and Irish, who established their claim to ancient lineage through literary references to Britain under the Romans and through adaptations of Latin epic. The ambiguity of Troy, represented by Aeneas as a figure of both heroic endeavour and treacherous betrayal, is addressed in different ways by English, Welsh, and Irish writers. The chapter ends with a discussion of the Trojan prefaces in Sir Gawain and the Green Knight and Chaucer’s House of Fame, suggesting that these prefaces are motivated comments on the questionable historical construction of English identity.