 After education and ordination in the monastery at Bangor in northern Wales, he became an active missionary with the support of Cadfan, king of Gwynedd.Cadfan's son and successor Cadwallon deceived Beuno about some land and, when the saint demanded justice, proved unsympathetic.Thereupon, Cadwallon's cousin Gwyddaint "gave to God and Beuno forever" his land at Clynnog Fawr on the Llŷn peninsula.