)[1] He appears only in the Life of St. Kentigern by Jocelyn of Furness, which regards him as a cleric, thus connecting him with the several obscure saints named Constantine venerated throughout Britain.
He is absent from the pedigrees of Northern British kings in the Harleian genealogies and the Bonedd Gwŷr y Gogledd (This is the Descent of the Men of the North).
[1] A Saint Constantine was venerated in the area around Glasgow, the setting of much of Jocelyn's narrative; the early church in the nearby burgh of Govan was dedicated to him.
[1] The compilation of hagiographies in the Orthodox Church known as the "Great Synaxaristes" includes Saint Constantine of Strathclyde, giving his feast day as 11 March.
Whilst there are no robust historical records of his existence, the available legend narrates that he abdicated the throne of Strathclyde in 612 AD to become a monk, and later a priest.