Later, Gwrgan features as king in charters in the Book of Llandaff associated with Bishops Oudoceus and Iunapeius.
Gwrgan is referred to as King of Damnonia by William of Malmesbury, who reports the terms of a grant of land made by him to the "old church" at Glastonbury in AD 601 in the time of Abbot Worgret.
However, the overlordship of Glywysing and Gwent may be indicated if he is identified with Gwrgan Frych (the Freckled) who features in the Life of Saint Cadog.
This powerful lord who ruled further west in Glywysing, granted the Saint half the fishing rights on the Rivers Usk and Neath in return for the great sword of King Rhun Hir of Gwynedd and a fine new horse with all the trappings.
It appears that his son-in-law, King Meurig of Glywysing and Gwent, managed to seize power in the name of his son, Athrwys.