The Once and Future King Book 3, Chapter 30
Sir Aglovale the son of the dead King Pellinore, then arrives. He tells Guenever and Arthur that he must kill Gawaine and his brothers because they killed his father, then he tells a story. His brother Percivale, who is kind and simple and devout, climbed into a magic boat with Bors and Galahad. On the boat, which can only be occupied by those of perfect faith, they find three swords: a great one for Galahad and a lesser one for the other two.
Before the story, Arthur tried to convince Aglovale not to start a long-lasting feud with the Orkney brothers, and now, Aglovale suddenly asks Arthur to invite them to dinner. Arthur is thrilled and very proud of Aglovale.