Episode 13 of 13. First transmission on Saturday December 19, 2009 (UK)
The official details about the episode are as follows…
The Great Dragon is finally free and, full of rage, attacks Camelot with pitiless intensity, in the final episode of the magical family drama. The castle is crumbling and Arthur’s men cannot hold out much longer. Only a Dragonlord can kill a dragon and Uther wiped them all out years ago – or did he? Gaius admits one such man could still be alive and in hiding.
The last Dragonlord is the key to Merlin’s own past as well as the future of Camelot, but will Arthur and Merlin find Balinor in time to save the kingdom and can they persuade him to return to Camelot to save his enemy, Uther?
The Great Dragon is voiced by John Hurt, Arthur is played by Bradley James, Uther by Anthony Head, Gaius by Richard Wilson, Merlin by Colin Morgan and Balinor by John Lynch.