From Caradoc of Llancarfan, Life of St. Gildas (ca. 1130)
Trans. Patrick Sims-Williams

Gildas . . . embarked in a little boat and entered Glastonbury, . . . while King Melvas was reigning in the Summer Region.  . . . Glastonbury, that is, the Glass City . . . was besieged by the tyrant Arthur with an innumerable multitude on account of his wife Guennuvar, who had been violated and carried off by the aforesaid iniquitous king, and had been brought there on account of the refuge of its inviolate position, which was due to the defences of its reeds, river and protecting marsh.  The warring king had sought the queen for a year, and at last heard that she dwelt there.  He moved there the armies of all Cornwall and Devon (Dibnenia); battle was made ready between the enemies.  Seeing this, the abbot of Glastonbury, accompanied by his clergy and Gildas the Wise, went between the lines of battle, and peacefully advised his king Melvas that he should return the abducted woman.  She who was to be returned was therefore returned in peace and goodwill.  This done, the two kings granted the abbot many lands.