Merlin Season 2 Episode 10

Rulers from the Five Kingdoms converge on Camelot for a peace conference , including King Olaf and his spoilt, over-protected daughter Vivian. King Alined is also present with his jester, the wizard Trickler, but he is a disruptive force who wants to cause discord between Olaf and Pendragon to gain the ultimate power for himself. To this end he gets Trickler to bewitch Vivian and Arthur so that they fall in love and incur the annoyance of Olaf, who challenges Arthur to a dual. This time it is down to Guinevere, rather than Merlin, to break the spell.