Merlin

*Merlin returns on Saturday, October 1 on BBC1*

BBC One's Merlin returns, with a thrilling two-part opener to the fourth series of the global medieval fantasy hit.

Merlin faces his toughest challenge yet when the blinkered determination of Morgana (Katie McGrath) threatens not only Arthur's future, but also the very balance of the world. With her magic stronger than ever, the sorceress summons the mighty Callieach (Gemma Jones) to tear open the veil between the worlds.

Hellish creatures pour forth, killing all who succumb to their touch. With Uther (Anthony Head) a shadow of his former self, it falls to Arthur (Bradley James) and his loyal knights, including Lancelot (Santiago Cabrera), to protect the kingdom.

But it will take more than just swords to vanquish their enemy and Merlin is shocked to the core when he discovers the only way to restore the equilibrium requires a sacrifice of unimaginable proportions...

Merlin also stars Richard Wilson as Gaius, Angel Coulby as Gwen, Nathaniel Parker as Agravaine, John Hurt as the voice of The Dragon, Tom Hopper as Sir Percival, Eoin Macken as Sir Gwaine, Adetomiwa Edun as Sir Elyan and Rupert Young as Sir Leon. Emilia Fox guest stars as Morgause.

Follow Merlin on his adventure through Camelot by logging onto whatsontv.co.uk