The way in which anger and violence were expressed in medieval societies is a subject of lively continuing interest. This article takes this focus as a means of considering how the cultures of early-thirteenth century native Welsh and Anglo-French secular elites may have differed, by comparing the literary portrayal of anger and violence in the History of William Marshal and the court poetry praising Llywelyn ap Iorwerth, which are broadly contemporary. Although the genres of these works are very different, reflecting the distinctive socio-political contexts in which they were produced, the differences in genre are themselves significant in illuminating the differing functions of the works. To assess their significance, the article sets detailed comparisons in the broader context of the many-stranded literatures of both cultures. The analysis underlines the extent to which Gwynedd's rulers needed to be culturally-amphibious if they were to pursue their strategic political objectives effectively, and also raises questions about the internal stresses likely to have been generated by cultural change within native Wales during the thirteenth century.