St Cadfan came from Brittany with several companions and founded a monastery at Tywyn, modern Towyn, in Gwynedd. There is a stone dating from the 8 or 9C in the church inscribed with his name which may have indicated his grave. There is also a holy well. He later moved further up the coast to the Lleyn peninsula and to Bardsey Island though he may not have been the first. It is likely he was buried there. Bardsey is a popular place of pilgrimage.
