A prince in Wales who desired to become a monk. Although this caused some outrage at the time he was eventually allowed to do this.
After the death of his brother, Queen Gwenwynwyn (his stepsister) wished for him to marry in order to place him on the throne of Powys.
He refused and, after his monastery was persecuted he fled to Brittany.
Peculiarly, he is now generally famed for his inclusion in the name of a small Welsh village called Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch.