He appears in four charters in the Book of Llandaff during the episcopate of Bishops Euddogwy and Inabwy. Later, Gwrgan features as king in charters in the Book of Llandaff associated with Bishops Oudoceus and Iunapeius.
In the Book of Llandaff, he appears in four charters during the episcopate of Bishops Euddogwy and Inabwy. Subsequently, Gwrgan is described as a king in charters from the same period associated with Bishops Oudoceus and Iunapeius.