Cadwaladr's name appears as 'Catgualart' in a section of the "Historia Brittonum", where it says he died of a dreadful mortality while he was king. The great plague of 664 is not noted in the "Annales Cambriae", but Bede's description makes clear its impact in both Britain and Ireland, where its occurrence is also noted in the "Irish Annals". The plague of 682 is not noted by Bede, but the "Annales Cambriae" note its occurrence in Britain and that Cadwaladr was one of its victims. Both the "Annales Cambriae" and the "Irish Annals" note the plague's impact in Ireland in 683, as do other sources.