The reason Launcelot is Guinevere's knight at the end of the tale is that he is "the best in the world": her judgment of him is, as always, the judgment of civilization. Within this tale it is not shown that Launcelot has been seeking from her anything more than this symbolic approval. Nevertheless, Launcelot's behavior, even his language, as well as his attention to Guinevere, is nobler and more polite than that of Arthur himself.
Malory does not develop the ironic and dangerous potential in all this; but the potential is clearly there. Malory alters his sources to make Launcelot send his prisoners to the queen rather than to Arthur, and he makes it clear that Launcelot's disguise as Kay actually fools no one. In the end, Kay has been made a fool of, and Launcelot has replaced him in Arthur's favor as well as the queen's.
In short, what appears on the surface to be an illustration of model knighthood is in fact, as Professor R. M. Lumiansky says, "a prelude to adultery," a central cause of the Round Table's fall. The final irony, which comes out more and more clearly as Le Morte d'Arthur progresses, is that it is chiefly Launcelot's need to prove himself to the lady he loves that makes him the great knight he is.
