St Keyne was a pious virgin, one of the many saintly daughters of King Brychan of Brecon. She may have lived at Keynsham in Somerset, but founded St Keyne in Cornwall, (among other sites) in the late 5th century, and left her name to a church and a well there, the latter (pictured above) whose waters are said to give the upper hand to whichever of two newlyweds does first drink the sacred spring's holy water. In 490 she visited her nephew St Cadoc at St Michael's Mount where legend states a granite chair or throne is said to grant matrimonial advantage.
References: A Guide to the Saints of Wales and the Westcountry, Ray Spencer. A Pilgrims Guide to the Holy Wells of Cornwall, J Meyrick.