Lancelot is a peculiar man with a contradictory nature: he likes to hurt people and is cruel; yet he fell in love with Guenever because he had hurt her.
Lancelot is one of the most complex characters in this novel—more so than Arthur.
When Arthur and Lancelot arrive in England, Lancelot quickly realizes Guenever would come between them: he sees her kiss Arthur and feels his entrails in knots. The next day, he asks Arthur if he might have leave from court, to quest and to use his Might for Right. In truth, Lancelot knows he needs to be away from Guenever, but Arthur grants him leave all the same.
White shows that it is inevitable that Lancelot and Guenever will betray Arthur—it is only time until they do. Thus the origin of Lancelot's questing is not purity, but rather to avoid an unavoidable betrayal. His questing—like all quests, the novel suggests—is futile.