Claim: Guinevere had an affair with a knight, Sir Lancelot.
Evidence: In medieval romances , one of the most prominent story arcs is Queen Guinevere 's love affair with her husband 's chief knight , Lancelot.
Sir Lancelot du Lac -LRB- meaning Lancelot of the lake , baptised as Galahad -RRB- was one of the Knights of the Round Table in the Arthurian legend.