Merchwyn Wylt, King of Gorfynedd
(Born c.AD 478)
(Latin: Marcianus; English: Mark)

Gorfynedd, the land to the east of the Gower Peninsula was, according to tradition, left by King Glywys of Glywysing to his son, Merchwyn. Known to eternity as Marcianus Vesanus or "Marcianus the Mad," he has a most unenviable reputation, and to a large extent has become confused with the evil King Mark of Cornwall. The Welsh version of this character, called March ap Meirchion, may have been based on or confused with Merchwyn. Like King Midas of Greek myth, this late 5th century king was said to have had horse's ears: a fact that was revealed every time he had a hair-cut. To keep this secret, he therefore murdered each of his barbers. That is until a local man made a set of pipes from reeds growing on one of the barbers' graves. Whenever he played them, they would sing, "March ap Meirchion has horse's ears".

Merchwyn's palace was traditionally at Llanilltud Fawr (Llantwit Major), so it is not surprising that he had several run-ins with St. Illtud whose renowned monastery stood in the same parish. In fact, it was Merchwyn who originally gave Illtud the land for his foundation. He is said to have met the saint, after a deer the King was hunting sought refuge in St. Illtud's hermitage. At first irritated because Illtud had built his cell without asking the monarch's permission, Merchwyn was later talked around; especially after a hearty meal in which the saint made the fish and water taste of whatever the King desired. Some time later, the two fell out after the King Merchwyn's steward tried to extract Royal tribute from the saint. The man soon found himself accidentally burnt to death, and Merchwyn immediately set out to wreak vengeance on Illtud. The saint fled to a secret cave in Ewenni. After several years there, Illtud returned, only to fall foul of the King's new steward. The royal officer confiscated the saint's cattle, but soon found himself drowning in a bog. Merchwyn arrived at the abbey once more to seek an explanation and found himself suffering the same fate.

Records of Merchwyn Wylt date back to the 7th century. He may well have been historic.