Maen Huail

Huail ap Kaw was the son of Kaw o Brydain, chieftain of Edeirnion — and though he was brave he was also wild and reckless beyond all wisdom. Weary of the shackles of law and peacetime, he raided Arthur's lands, abducting, stealing and bringing misery to the people. Arthur pursued Huail, and finally caught him in what is now the square at Rhuthun. When the two men met blade to blade, in a typical display of chivalry and fair play, Arthur drove Excalibur into the stone in the market square and fought with a common sword forged by a mortal. Despite defeating Huail, Arthur suffered a stab to the knee. As Huail lay defeated, his head on the stone, he pleaded for his life, and Arthur granted this to him on condition that he swore an oath to cease raiding and obey the law.
However, Huail was untameable and without respect. He began raiding again, and Arthur returned to Rhuthun to defend it. At an evening dance, Huail infiltrated Arthur’s ranks unnoticed. However, he could not stop himself mocking Arthur: ”Da iawn yw downshio velly oni bai'r glun" — "This dancing were all right, if it were not for the knee”, he mocked.
Arthur turned, recognising the voice. Now Arthur fought him back to the stone, and there he cut cruel Huail’s head from his body.