Merlin - His Father's Son

Arthur is now King of Camelot and his first issue is a neighbouring kingdom trying to enter his lands.  He sets a trap and captures one of the knights of Caerleon, who ends up being the King.  Agravaine manipulates Arthur, chiding him that he needs to be more like Uther and that he must execute this other King.  Against his better judgement, and the advice of Merlin, Arthur kills King Caerleon and send his body back to his Queen.  Queen Annis is enraged and declares war on Camelot, raising an army and heading off to kill Arthur.  Arthur has no option now but to go to war.  While still not sure of himself, Arthur is manipulated again by agravaine who tells him he must end the relationship with Gwen if he is to be respected as the King.  Arthur goes to Gwen and tells her they are over.
Meanwhile, Morgana decides she will take advantage of the war and side with Queen Annis, to help her rid her of Arthur once and for all.
Arthur arrives at the battlefront and after seeing the size of Caerleon's army, he realises that many of his men may die because of the decision he made to kill the King.  He realises he made a terrible mistake and must fix this.  He goes to see Queen Annis and invokes the right to single combat to decide the victor.  If Camelot's champion wins, the Queen must leave, if Caerleon's champion wins, they will get half of Camelot.  The Queen agrees.  Instead of choosing one of his knights, Arthur decides to face the chamion of Caerleon himself.
In order to defeat him, Morgana enchants Arthur's sword so that he cannot even pick it up when she releases the magic.  The champion of Caerleon is a huge man and when he cannot use his sword, Arthur must use his fists, along with Merlin's unknown assistance.  Arthur defeats the champion, and instead of killing him, he shows him mercy in the hope that there could be peace between their kingdoms.
Queen Annis complies with the terms and agrees to peace and spurns Morgana.
Arthur returns to Camelot and apologises to Gwen, sho forgives him.
This was another great episode of Merlin, with a great story (a bit brutal for Arthur though) and some fantastic special effects.  Really loving this show.