St Gwynllyw (Gundleus, Woolos) was a Welsh king of Gwynllwg in Glamorgan in the 5C; he and his wife St Gwladys, also a royal, were the parents of St Cadoc who converted them. Both are said to have become hermits. Upon the death of St Gwynllyw his cell became a popular shrine; eventually, in the 9C, a stone church was built on it where the cathedral of St Woolos now stands on Stowe Hill, Newport. The Life of St Gwynllyw tells of many miracles. The miracles worked at his tomb made it a famous place of pilgrimage.
St Gwladys may have had a hermitage on the west side of Newport. She is said to have been buried on Gelligaer Common in Caerphilly where the ruin of a mediaeval chapel lies marked by a modern cross. A 10C cross was found here in 1906 and is now kept in the church at Gelligaer in South Wales.