Doctor Who: Twice Upon a Time spoiler-free preview

• Karen Gillan would have loved to be a companion to a female Doctor in Doctor Who
• David Bradley has enjoyed a lifetime of Doctor Who – now he’s bringing the classic series back to life
• What are Steven Moffat’s Desert Island Doctor Whos - and why did Matt Smith “punch his pillow in frustration”?

This Christmas Day, millions of people around the world won’t be tuning in to watch the usual seasonal sci-fi frolic. Instead they’ll be waiting for the last 30 seconds, when Capaldi’s craggy features are bathed in golden light and morph into the face of Whittaker, dragging the series into a whole new age.

Still, audiences tuning in for those final moments will still have an hour of story to wait through, so it’s good that Twice Upon a Time is as fun, imaginative and sweetly sad as it is, capping off Capaldi’s time on Doctor Who with less of a glorious final stand (series 10 finale The Doctor Falls took care of that) than an offbeat epilogue where the Doctor decides to rise once again.

“I don’t want to go,” were the famous last words of David Tennant’s Tenth Doctor way back in January 2010, during a similar period of upheaval in the series – but nearly 8 years later, they apply almost just as perfectly to Peter Capaldi’s incarnation as he struggles once more against his change into a new face.

However, this time he’s not alone in his pain, joined by his very first incarnation as THAT Doctor also tries to put off regenerating into a new form. Taking over as the First Doctor from original 1960s actor William Hartnell (who does appear in some archive footage), Harry Potter star David Bradley does a great job at embodying the late actor’s spirit, even if it’s not a direct match at times (for the canon completists, there’s also a throwaway explanation for why Bradley’s face looks so different from Hartnell’s).

As many will have already witnessed in the above preview clip released for Children in Need, the chemistry between the two Time Lords is terrific, and involving the First Doctor is a great way to make this episode FEEL momentous despite not that much actually happening story-wise (of which, more later). Bradley’s also brilliantly funny in the role, mining the First Doctor’s political incorrectness and slightly sterner outward persona for laughs throughout the episode even if one or two of the slightly sexist gags (volubly protested by Capaldi’s more PC Doctor) do start to grate as the episode goes on.

And of course, Bradley’s not the only sidekick to Capaldi’s Doctor in the frame this year, with Pearl Mackie’s Bill Potts back in the Tardis after seeming to leave forever at the end of the last series. The back-and-forth between Miss Potts and the Doctor works as well as ever, and while Mackie’s arc is a little unusual in the episode it’s still a nice final showcase for her wonderful performance as Bill, a character who seems to have been a sad casualty of the big changes in Doctor Who this year.

Joining the three of them on their adventure is regular series actor/writer Mark Gatiss as a character I can only call The Captain, who fits in nicely enough as an honourable man of war swept along with the time-travelling shenanigans.

When it comes to the story itself, there’s not too much I’d want to spoil – as has been revealed by official synopses, it involves a glass woman chasing individuals through frozen time – but I will says it’s a surprisingly slight tale, mainly focusing on the interactions between the Doctor and his friends over spectacle or timey-wimey plot complications.

It’s in sharp contrast with writer Steven Moffat’s last Christmas regeneration episode The Time of the Doctor, which took place over centuries and saw the entirety of departing Doctor Matt Smith’s time on the series reflected in the blockbuster story. Twice Upon a Time does nod to a few past adventures of Capaldi’s Doctor, but there are a few surprising absences and generally speaking it pleasantly trots along rather than sprinting to the finish line.

In fact, if you look back on the events of the episode surprisingly little happens at all, even compared to the fluffier standards of your average Who Christmas special. This isn’t necessarily a bad thing, though, as it gives Capaldi’s final regeneration scene a lot more room to breathe – and it is a corker.

Unlike many, I wasn’t a huge fan of Matt Smith’s regeneration scene, or even David Tennant’s slightly drawn-out goodbye, but Capaldi’s exit has real power behind it. After leaving his compatriots behind (Bill’s absence from her Doctor’s last moments does make sense in the context of the episode), Capaldi spends his final minutes alone delivering a barnstorming address that tries to define his complicated Doctor one last time, finding humour and gravitas even as exhaustion and sadness threatens to overwhelm him.

It’s a moving coda to both Capaldi and Moffat’s time on the series, and an invigorating end to a solid episode. Even the people just waiting to see Jodie Whittaker might find themselves shedding a tear or two.

Doctor Who: Twice Upon a Time airs on BBC1 on Christmas Day (Monday 25th December) at 5:30pm