Series three of Merlin began on 11 September 2010. Series three regular cast members include Colin Morgan, Bradley James, Katie McGrath, Angel Coulby, Anthony Head, and Richard Wilson, as well as Emilia Fox joining the regular cast. John Hurt took his previous role as the voice of the Great Dragon but was no longer one of the regular cast (though he continued to provide the opening narration for the series). Series three consists of 13 episodes. The series three premiere was watched by 6.49 million viewers.
The season was notable for the change in character of Morgana from the sympathetic heroine in the first two series to the villain in series 3, keeping with the historical concept of Morgan Le Fay as Merlin's nemesis in the legends of King Arthur.