A duel between King Olaf and Prince Arthur occurred in the midst of the Peace of the Five Kingdoms negotiations. The duel was instigated obliquely by King Alined, whose servant, Trickler, had given love potions to Arthur and Vivian, knowing that Arthur's infatuation with Vivian would incense Olaf.
The duel was fought at the Duelling pitch in three rounds: the first round was fought with quarterstaffs, the second round was fought with maces, and the third round was fought with broadswords. Merlin managed to undo the love enchantment on Arthur before the prince killed Olaf in the duel, and the act of sparing the king's life was sufficient to bring Olaf back to the negotiations table (Sweet Dreams).
Victory: Arthur Pendragon