Armes Prydain Fawr ‘the Great Prophecy of Britain’ (APF henceforth), dated to the second quarter of the tenth century, is a vaticinatory poem of 199 lines, preserved in NLW Peniarth MS 2, known informally as ‘The Book of Taliesin’. An edition, a translation and an analysis of the thematic structure of the poem will all be presented below. the poem expresses, in the form of prophecy, dissatisfaction with the interference of the English king Aethelstan (apparently) in Welsh affairs, principally by means of a tax. This implies simultaneously protest against the policies of Welsh rulers, most prominently Hywel Dda, to accept that tax and interference in return for being left alone to pursue their own dynastic agendas. The poet places these protests in the context of a scathing attack on the nature of English rule in Britain in general, how they treacherously came to power and ousted the Britons, and how they will ultimately be driven back to where they came from in a glorious rebellion led secularly by the legendary saviour-heroes Cynan and Cadwaladr, and spiritually by St David.

It is correct to state that APF contains the earliest references to St David in (extant) Welsh literature. What earlier references there are to him at all are found in chronicles, a catalogue of saints, martyrologies and calendars, with various passing references to him in lives of other saints, and Asser's references to him in the Life of King Alfred.