The Once and Future King Book 4, Chapter 5

Gawaine, Gaheris, and Gareth try to dissuade the other brothers from telling Arthur about Guenever's affair. They worry that the accusation would start a war, and split the family apart-little do they know that this is exactly what Agravaine and Mordred want. Gawaine tries to make up with Agravaine, and the three try to defend Lancelot against the other two. Absurdly, Agravaine and Mordred claim that Lancelot only does good deeds for his own honor-though Mordred admits that he doesn't care about Lancelot particularly; Arthur is the one he hates. Arthur enters the room, and the three assure him that what their two brothers are about to say has nothing to do with them. Agravaine and Mordred press on, accusing the Queen to her husband's face. Arthur says that, if they can provide evidence of the affair, he will unfortunately (for justice's sake) be forced to punish Lancelot and Guenever. However, he assures them that if they cannot prove it, he will punish them as severely as justice allows. Through all this, Agravaine has been hesitant-he may not like Lancelot, but he's not sure if he wants to start a war-but Mordred is unstoppable. He obviously does not care at all about the King's honor (the supposed reason he is accusing the Queen in the first place). He is doing this out of hatred for the King, and as a ploy for power.