The Once and Future King Book 3, Chapter 26
Lancelot and Arthur talk about the state of the court. Gareth and Mordred have both run away from Morgause to be with Arthur, which has enraged their mother. Lancelot dislikes Mordred instinctively. Lancelot tells Arthur that Morgause is having an affair with Lamorak, the son of Pellinore-even though Pellinore killed her husband (by accident). Arthur is terrified of what Gawaine and the rest will do to Lamorak, since they were such a close family. Arthur claims that he has established the Round Table by force, even though doing so went against the very purpose of the Table, and that now he will be punished for it. Sure enough, Gareth arrives to tell them that Agravaine has murdered his mother after finding her in bed with Lamorak. Then Gawaine, Agravaine and Mordred hunted down Lamorak himself.