Lancelot

Sir Lancelot du Lac (meaning Lancelot of the Lake, baptised as Galahad) was one of the Knights of the Round Table in the Arthurian legend. He typically features as King Arthur's greatest champion, the lord of Joyous Gard and the greatest swordsman and jouster of the age — until his adultery with Queen Guinevere is discovered, causing a civil war exploited by Mordred which brings about the end of Arthur's kingdom.