A comprehensive and objective study of Layamon's sources is long overdue. As a first step Françoise le Saux investigates the English poet's handling of his main source, Wace's Roman de Brut, to determine what principles guided the composition of the English Brut. These established, she is able to distinguish between different sorts of variation from the Roman, thereby providing norms against which to gauge the probability of further, secondary sources. Additional sources are then identified, in the various fields suggested by the poem: historical; literary; and religious writings (or tales) in Welsh, English, Latin and French and perhaps even Scandinavian.