Gildas, who calls him king of Damnonia
The historical Constantine of Dumnonia may have influenced later traditions, known in Southwestern Britain as well as in Wales, Ireland, and Scotland, about a Saint Constantine who is usually said to have been a king who gave up his crown to become a monk. The Cornish and Welsh traditions especially may have been influenced by Gildas’ screed, in particular his adjuration for Constantine to repent; the belief may have been that the reproach eventually worked.
The two major centers for the cultus of Saint Constantine were the church in Constantine Parish and the Chapel of Saint Constantine in St Merryn Parish (now Constantine Bay), both in Cornwall. The former was established by at least the 11th century, as it is mentioned in Rhygyfarch’s 11th-century Life of Saint David. At this time it may have supported a clerical community, but in later centuries it became simply a parish church. The Chapel at Constantine Bay had a holy well, and was the centre of its own sub-parish.
The Annales Cambriae (Welsh Annals) and the Annals of Ulster record the conversion of a certain Constantine; these may be a reference to the Cornish saint and therefore to the historical figure. A number of subsequent texts refer to Constantine, generally associating him with Cornwall, often specifically as its king. The Life of Saint David says that Constantine, King of Cornwall gave up his crown and joined Saint David’s monastery at Menevia. The Vitae Petroci includes an episode in which Saint Petroc protects a stag being hunted by a wealthy man named Constantine, who eventually converts and becomes a monk. Here Constantine is not said to be king, but a 12th-century text referring to this story, the Miracula, specifically names him as such, further adding that he gave Petroc an ivory horn upon his conversion which became one of the saint’s chief relics. These references are only a few to the various shadowy saints and kings named Constantine attested across Britain, and suggests a confusion and conflation of various figures. (more)