Saint Meurig (Maurice), son of Saint Tewdric (or Tewdrig), was the king of Glamorgan (and Gwent?) sometime between the mid-500s and 700 CE1. According to the Book of Llan Dâv2 (see Other Works) Tewdric gave the crown to his son and retired to Dindyrn (Tintern) as a recluse after a lifetime as an undefeated warrior.
However, the Saxons threatened to invade and take his son's territory, so Tewdric took to the battlefield one last time, assured by an angel of the lord that he would die, but die victorious. This came to pass, and the old king was wounded, however he refused to die until Christ took him to the Isle of Echni (Flat Holm Island?**) to be buried. Duely, the next morning, two stags yoked to a carriage appeared and bore him towards the Severn3. At a meadow near the river the carriage broke and a clear spring flowed (though it is not clear whether this was because of Tewdric or was there before). He ordered the stags away and expired. His son then had built there a prayer-house and cemetery, which he then gave, along with the whole area, to the church of Llan Dâv (History) - or so they say...
The spring is universally believed to be St.Tewdric's Well in Mathern, while the church is held to be St.Theodorick's (a latinization of Tewdric[k]), again in Mathern, next to the palace of the Bishops of Llan Dâv.