Comprising 13 episodes, it once again stars Colin Morgan as Merlin, Bradley James as King Arthur, Angel Coulby as Gwen, Katie McGrath as Morgana, Richard Wilson as Gaius, and John Hurt as the voice of the Great Dragon.
Tom Hopper, Rupert Young, Eoin Macken, and Adetomiwa Edun return as The Knights of the Round Table, and special guest stars will include Liam Cunningham as Ruadan, Lindsay Duncan as Queen Annis, and Sophie Rundle as Sefa. In addition, Anthony Head will return for one episode as Arthur's father, Uther Pendragon.
But even as Camelot flowers, so the dark seeds of her destruction are being sown. For in the frozen wastelands of the North, men are disappearing without trace. In search of answers, King Arthur and his Knights must undertake a dangerous mission to the unknown.
UPDATE (4pm): BBC One has been running trailers for Merlin this afternoon with the voiceover announcing that the series is beginning on "Saturday 8th October" and the caption card also stating "8th October". A phone call to BBC TV Centre to point out that 8th October is, in fact, a Monday and to seek clarification over the start date resulted in the admission that a mistake had been made by the production team and that they were seeking to remedy the matter as soon as possible. The spokeswoman confirmed that the series would be starting on Saturday 6th October.