A knight whose wife, Dyagenne, was loved by Uther Pendragon (after the latter’s marriage to Igerne). Argan discovered their affair and challenged Uther, defeating him in combat. Argan spared Uther’s life but slew Dyagenne. As a condition of Uther’s surrender, Argan made him build an impenetrable castle called Uther’s Shame.
Argan re-married, but was cuckolded and defeated by Hector, Lancelot’s brother. Enraged, Argan built the Red Tower Bridge and tried to defeat any knights who wanted to cross. This custom was continued by his four sons.
Source
Prose Tristan | 1230-1240