The Once and Future King Book 3, Chapter 5
Lancelot and Guenever fall in love, and King Arthur and Uncle Dap notice it immediately. Dap gives Lancelot a lecture about throwing away his jousting career for a woman. Lancelot denies it, trying to cling to his virtue. Arthur isn't sure what to think-Merlyn has warned him about this, but he can't quite believe it. So he decides to take Lancelot with him on a war, away from Guenever. Lancelot is annoyed at this, because, since at this point Gawaine is the captain of the knights, the only reason Lancelot would go along is to be kept from Guenever. During the war, both of them grow more fond of each other, and decide mutually that Guenever should never come between them.