It’s the penultimate ever episode of Merlin and naturally expectations are extremely high, so how does the first half shape up?

The story kicks off with Morgana and her new right-hand man Mordred preparing to hit Arthur where it will hurt him the most. Fresh with the knowledge of Emrys’ real identity, Morgana now knows that by taking out Merlin first, Arthur will be crippled. And so her final plan is put into action…

Things are surprisingly jovial back in Camelot with Merlin and Arthur down in the tavern indulging in a game of dice – a moment of calm before the storm. Events soon take a turn for the worse when Merlin stumbles back late at night and is attacked by a horrible slug-like creature, robbing him of his magic ability.

When Morgana subsequently launches an attack on Camelot’s borders, Arthur knows he must respond in kind and prepares for war. With no magic, Merlin has to reluctantly leave Arthur to go into battle without him, while he peruses a quest that takes him right back to the heart of magic.

Whereas the last few episodes have been slower and focussed on key individuals, here everyone gets a piece of the action and the plot moves along at a fair pace. Gwaine in particular gets a more enhanced role, and Eoin Macken’s charm wins through again. We also meet his love interest Eira (guest star Erin Richards), a character who has more going on than meets the eye.

Merlin is more vulnerable than ever in this episode and he may just bring a tear to your eye in one scene. There’s a moment where you feel immense sympathy as he is completely helpless. We’ve been singing Colin Morgan’s praises all series and he delivers another solid performance throughout. As for Arthur, Bradley James gets to play some nice scenes with both Morgan and Angel Coulby, not to mention a rousing battle speech.

Morgana is at her most unstable yet and she gets a long-awaited confrontation with Merlin that’s frustratingly cut short (think of it as Round One though). It’s a little disappointing to see Mordred reduced to a mere sidekick after such a standout role last week, but that’s more an issue of time than anything. There’s a lot to cram in here.

The episode contains a couple of nice throwbacks for long-time fans, with some flashback scenes and a face from Merlin’s past returning at just the right moment. If you’ve been following all the spoilers then you’ll have a good idea who it is, but for everyone else it’ll be a nice surprise.

Overall, it’s a compelling set-up for the final episode. Those hoping for major revelations may be disappointed as they are inevitably being held back for greater impact in the final episode. Only there will we be able to tell if there’s enough time for everything to have a satisfactory wrap up. It was certainly a wise choice to air both episodes so close together though, as the ending leaves things on a cliffhanger that will have you itching to find out what happens next…

8/10

Part 1 airs Saturday 22 December 7.55pm on BBC1.