Riwal Mawr Marchou, King of Domnonée
(c.AD 480-520)
(Welsh: Rhiwallon; Latin: Rivaldus; English: Riwald)

Riwal the Great Knight appears in the 'lives' of a number of Breton saints where he is recorded as the son of Deroch I map Guitol. However, other details of his life and relationships suggest that he lived at a later period and may have been accidentally been trasnposed with his grandson in the pedigrees, Riatham, who was the son of Deroch II.

Riwal is said to have hailed from Britain and to have emigrated to Brittany with a large number of followers. This, however, probably relates to one of his ancestors. In Brittany, Riwal found it politic to pay homage to King Chlothar I of the Franks, as well as perhaps his cousins in Cornouaille, in order to secure his position. This places him in the early 6th century.

Legend tells us that, when Prince Fracan of Kernow (Cornwall) settled in Domnonée, he quickly had a set to with his new monarch. Riwal claimed to have a much swifter horse than Fracan, but the latter could not agree. They organised a race to decide whose beast was the best, but the new arrival's jockey fell and was nearly killed. Luckily, Fracan's son, St. Winwaloe was able to heal him. Riwal may have been impressed by this saint's miracle working for he became a patron of the church and gave much land to his 'cousin' (actually his nephew), St.Brioc.