The duel between Merlin and Arthur occurred after Arthur had Merlin imprisoned for objecting to the way he was treating his servant.
Events
Soon after Merlin was released from the dungeons, he encountered Arthur in the street and Arthur challenged him to a duel with maces. Merlin accepted, as he wanted to teach Arthur a lesson.
Arthur quickly gained the upper hand and cornered Merlin, who responded by defending himself with magic. He moved objects to make them obstacles and tripped Arthur with a length of rope, then seized Arthur's mace and began to taunt him. However, Merlin became distracted by Gaius, who had been watching the fight, and Arthur defeated him by attacking him from behind with a broom.
In the aftermath of the duel, Merlin was seized by Arthur's guards, but Arthur ordered that they release him and sent him on his way (The Dragon's Call).
Trivia
- After he revealed his magic to Arthur, Merlin admitted that he'd used magic during this duel and Arthur accused him of cheating (The Diamond of the Day).