Doctor Who Christmas specials often operate by different rules than the regular episodes. With certain obvious exceptions, they stand-alone, outside the regular continuity and generally avoiding any season-arc material. They frequently have a more exuberant tone and often feature a more extravagant guest-cast than usual. While disregarding a great many elements which made previous seasons of Nu-Who so successful, Chris Chibnall has been careful to make sure that at least some baby is retained, while the bathwater goes gurgling down the plug-hole.

In some respects, Resolution is a rehash of 2005’s stunning Dalek, the moment when I suddenly realised that Doctor Who in the twenty-first century could work. In each case, we have a single Dalek, brought back to life by well-meaning humans, which proceeds to lay waste to everything in its path, before the Doctor finally stops it in its tracks. Robert Shearman’s script isn’t perfect either, and the production team in 2005 is still finding its feet, but the differences between the two stories are instructive.

First, in Chibnall’s most brilliant innovation (possibly of his whole run to date), it’s the Dalek mutant which is brought back to life. The slightly portentous not-technically-a-pretitles-sequence-because-again-we-have-no-titles has echoes of the opening of The Battle of Rancorous Cornflakes – but is an effective scene-setter. And the relationship between Lin and Mitch is nicely handled. What’s the most effective part of the whole episode is the sight of Charlotte Ritchie, possessed by this alien parasite which gradually takes control of her more and more thoroughly.

I’m going to gloss over the fact that Dalek mutants apparently don’t actually need so-called “survival” machines any more, which seems a very boring thing to complain about given the upsides. All of this works gangbusters, with the Doctor’s pursuit of the creature not requiring her to be stupid in order to keep her one step behind, and the body horror nicely judged for a family audience. The ruthlessness of the Dalek and the horror than Lin experiences are very strong, but never overwhelming or off-putting. And the custom-built Dalek casing when it materialises is great, and let’s a have a mention for the hugely funny and enjoyable scene in which UNIT has been killed by Brexit. What’s less amusing is the over-familiar, patronising and childish “joke” about people’s internet being cut off. All right, grandad, I won’t watch your Doctor Who episode on iPlayer then. FFS.

So here’s the second big difference between this episode and Dalek. Every so often, this exhilarating science-fiction action-adventure gets intercut with a much less interesting, sub-Broadchurch family drama, in which cliched mopey teen Ryan turns out to have a cliched deadbeat Dad. (Think Pete Tyler but much less interesting). Daniel Adegboyega isn’t really given much to do, but his big scene with Bradley Walsh is good. What’s little short of bewildering is the seemingly-random swapping in-and-out of TARDIS occupants in order to allow the “right” people to interact at the right time. Of course, the other function of this thinly-drawn and off-theme second plot strand is to deposit Chekhov’s microwave at the Doctor’s feet. So let’s have a talk about the ending.

Setting up an unstoppable foe makes for a very exciting middle. But when you need your story to conclude, you have to stop the unstoppable. It’s a difficult storytelling problem, to say the least. The ending of Dalek doesn’t have the same kind of high-octane excitement that the rest of the story does, but it’s rooted in character and emotion. It’s all about who a Dalek is, at its core. And it’s about who the Doctor is, especially this new Doctor, suffering from survivor’s guilt. Because of the interplay between these three well-defined characters – the Doctor, the Dalek and Rose – the Dalek’s reason to exist is violently yanked away from it, and so it ceases to exist. But not without getting in one last devastating jab: “You would make a good Dalek.”

What solution does Chris Chibnall find? Run around behind it and microwave it to death. Sorry, what? With all the equipment on board the TARDIS, it’s impossible to disable a Dalek without a defrost setting?

And if you want to talk about overstuffed TARDISes, this is ridiculous. The Doctor, Yas, Ryan, Graham, Mitch, Lin and Aaron all have to gang up on it, but the plan really only requires one to distract it and one to stick the magnetron on it, so once again, the supporting cast get nothing to do Ryan and Graham get one scene each with Aaron (which as noted neither propels nor illuminates the main plot) and Yas gets exactly nothing.

There’s a second climax after that one, which makes even less sense and which undoes a lot of the good work in the first three quarters of the episode, so this is still recognisably Season 11 stuff – clumsily structured, with no thematic unity, an underused regular cast and thinly drawn supporting characters. But it’s also Chibnall’s best script of the season, and Jodie Whittaker has never been better in the central role.

Leave Yas, Graham and Ryan at home. Make Mitch and Lin temporary companions. Find a Dalek weakness other than consumer electronics and have the win come at some kind of cost (even Lin survives, which I suppose is fair enough for a celebratory episodes, but it does seem unlikely) and this might have been an absolute classic. As it is, four stars.

4 out of 5 stars