From the outset, Historia Brittonum establishes that Britain is an island of four gentes (§8). But it was not always so. Each gens ultimately came from elsewhere, reaching the island at different points in its history. The Britons were first, having journeyed from Troy via Italy and Tours, as discussed in the previous chapter. The Picts and the Irish came next, followed by the Romans for a passing visit. It was only much later that the Saxons arrived. This is not simply a chronological framework for understanding the settlement of Britain in Historia Brittonum: it is a key part of the identity of each gens as presented in the text. The chronology of migration and settlement is central to Armes Prydein too, not only as a means of interpreting the past, but also a way of dictating the future. In short, some migrations are more legitimate than others.

It is not simply the timing of settlement that is important, however, but also the manner through which land is obtained. The poet of Armes Prydein, for example, dwells on the treacherous methods used by the Saxons to seize the island from the Britons. Nennius outlines the origins and settlement of all three gentes and, as with the Trojan origin legend, these accounts construct the identity of their subjects in a specific way. There are clear implications too for the identity of the Britons, who are defined in relation to – and through interaction with – their neighbours. The settlement of the Saxons in particular is a long-drawn-out affair, involving conflict, co-operation, and treachery, and there is a need for flexibility in defining its parameters – certain origin legend motifs only occur quite late in the narrative. This chapter will examine this origin legend but will consider too Historia Brittonum's account of relations between the Britons and the Saxons in the sixth and seventh centuries in the ‘Northern History’; as with Roman Britain and the Trojan origin legend, this is an illuminating additional context. The discussion begins, however, with those who arrived first: the Picts and the Irish.