★★★★★ Yes, I know, another five stars… but you can tell a Doctor Who episode is a winner when you watch a very rough-cut version and it still hooks you. The first preview let out of the blocks had many fx missing and needed final edits and polish, as the production team strove to hit a tight deadline just a few days before transmission. Phew! 

The end is in sight for Messrs Moffat and Minchin, outgoing executive producers, and their remarkable cast (Peter Capaldi, Pearl Mackie, Matt Lucas, Michelle Gomez and John Simm) all signing off here, or soon... But what is perhaps most surprising about this concluding episode of Series Ten is how inconclusive it is.

The Mondas colony ship remains stuck on the threshold of a black hole. Its inhabitants are still under threat from incipient Cybermen. No one cause is specified for the Doctor’s regeneration, although he can evidently now hold the process at bay. And what is subtly needling is that the main characters remain unaware of each other’s fate. Nobody knows whether any of their friends or enemies have survived.

Nardole lives but is stranded on the spaceship. Will he or his party ever escape? The Doctor has no idea that Bill was restored/transformed by Heather nor that they returned him to the Tardis. Bill leaves without knowing that the Doctor will survive or even that he can regenerate. What, for me, is most poignant is that the Doctor does not know he succeeded in turning Missy from the dark side, that his best friend was returning to support him and may have died in the attempt. 

The Doctor Falls is an uneven but utterly engrossing “final” episode. Our hero thwarts, or at least tampers with, the Master’s fiendish plan remarkably early so that the First Act is wrapped up before the 15min mark. The Time Lords find themselves on the run from the Cybermen, and the action shifts from dystopian Floor 1056 to bucolic Floor 507. Suddenly the Doctor has a children’s refuge to protect. This change in pace and environment may be unexpected but it gives the characters pause to think and have difficult conversations. It gives the cast chance to shine. 

Capaldi, Simm and Gomez are of course divine together. Peter Capaldi is magnificent as ever. This is truly his episode. His Doctor may fall but he stands tall among stiff competition. John Simm’s Master is an implacable bastard to the end but not the loon of seven years ago. Michelle Gomez is simply superb at the duplicity and the soul-searching and laughing at her own tragedy. Their dancing, flirting and backstabbing is to die for.

There was fevered speculation over Sam Spiro’s casting. All sorts of daft notions. In the event, Hazran has no dark secret, other than she’s a love interest for Nardole. She’s a mother figure for the children under threat on Floor 507, toting a rifle at her homestead, putting me in mind of Lillian Gish in the 1950s movie classic The Night of the Hunter. 

I’m pleased that Bill earns a reprieve. Let’s not whinge that yet another regular character is seen to die or suffer a fate worse than death and then becomes undead. It would be horrible to leave her trussed up in those Cyber bandages. It has to be said Bill’s departure is remarkably similar to Clara’s at the end of series nine. Clara’s death was “paused”, her heartbeat frozen, and then she zoomed off into time and space in the company of another eternal woman (Ashildr/Me), leaving the Doctor none the wiser. Almost identical. 

I never foresaw Heather’s return and I tingle at the rapprochement of her romance with Bill. “I’m the Pilot. I can fly anything. Even you,” says Heather. “You’re like me now. It’s just a different kind of living.” You’d have to have a cold heart not to be persuaded and moved. “I left you my tears, remember,” is such a strange but beautiful notion. Bill deserves this ending. And Pearl Mackie plays it to perfection.

Talking of talented women… Rachel Talalay isn’t simply a director, she’s an artist working in the medium of television. From the furnace of Floor 1056 to the Cotswold-y homestead to the snowy South Pole, she weaves varying tones and textures and tableaux, Quiet Moments and Big Moments, into one coherent, impressive tapestry. 

In her hands, any potential awkwardness of the “Bill doesn’t see herself as a Cyberman” scenes is ironed over. There’s the storyboard precision of Missy turning to camera as she’s shot and irradiated by the Master. The overhead angle of Missy breathing her last, looking like Ophelia, in that twilit blue-green woodland is one of many weirdly beautiful images. And there are lots of little touches. The way that Nardole in his final shot walks towards and beyond the camera and into his future, which cuts to a high-up drone shot of CyberBill staggering through a battle-scarred wasteland. 

Steven Moffat said this finale would not be a nostalgia fest. I don’t know whose leg he was pulling. It may not be a fest but it’s definitely a running buffet, with lots of savoury morsels to set off your nostalgic taste-buds. Capaldi’s Doctor is so like Jon Pertwee’s here, in looks and deeds, interacting with the Master, detonating explosions with his sonic screwdriver, heroically vanquishing the Cybermen while listing their past defeats.

One notable touch is that the original Cybermen never used their headlamps as a weapon, although they seemed to in an illustration on the back of the 1970s novel of The Tenth Planet (right). Were The Doctor Falls a book, there’d be copious footnotes – especially those pointing out allusions to the past. 

The Doctor remarks that the Cybermen “happen everywhere there’s people – Mondas, Telos, Earth, Planet 14, Marinus.” The first two were their home planets in the 1960s episodes. A parallel Earth gave rise to Cybermen during Russell T Davies’s tenure. Planet 14 is a fabulously obscure reference to a few lines of dialogue in The Invasion (1968). And Marinus? Well, that’s a nod to the 1964 serial The Keys of Marinus. (Perhaps Steven is suggesting that the rubbery Voord and semi-robotic Ice Soldiers encountered by William Hartnell’s companions were a form of Cybermen…) 

As the Doctor fights to stem his regeneration, there’s a St Vitus dance of nods to earlier regen episodes. His babble about Sontarans perverting the course of human history was Tom Baker’s first line in 1974. He revisits David Tennant’s excruciating bleat, “I don’t want to go,” and Matt Smith’s “[I will always remember] when the Doctor was me.” Bill’s line as she sobs over the Doctor, “While there’s tears, there’s hope,” echoes the Pertwee Doctor’s last words as Sarah sobbed over him: “A tear, Sarah Jane? No, don’t cry. While there’s life there’s…” The overhead shot of Bill and the Doctor, sprawled on the Tardis floor, cloaked splayed, echoes William Hartnell’s final moments in The Tenth Planet (below).  

And finally that ending. Nostalgia Central! Doctor 12 meeting Doctor One in the snowy wastes of Antarctica. “Où sont les neiges d’antan? / Where are the snows of yesteryear?” If you have un peu de French poetry or studied Rossetti or Tennessee Williams, you’ll know this scene uses one of literature’s key nostalgic motifs. 

We’re right back to the setting of The Tenth Planet 51 years ago. And a familiar figure, an old man in cloak, astrakhan hat and white scarf emerges from the blizzard. “You may be a Doctor but I am the Doctor,” he says, clutching his lapels. “The original you might say.” (This is a glorious mash-up of one of Tom Baker’s first lines in 1974 and Richard Hurndall’s as the first Doctor replacement in The Five Doctors in 1983.) 

How magical to see David Bradley again, not just playing William Hartnell (or even playing Hartnell as the first Doctor) as he did in An Adventure in Space and Time. Now he’s giving us his first Doctor. I knew full well this special moment was coming but it still touches the fanboy in me deeply.

Usually I approach the Christmas specials with trepidation. Not this time. I can’t wait to see Peter Capaldi and David Bradley performing side by side.