Playing around with an icon as beloved as the TARDIS is something which can earn you serious fan love, as with 2011’s ‘The Doctor’s Wife’, or something closer to anticipointment, as with 1978’s sometimes regarded, sometimes disregarded ‘The Invasion of Time’.

Understandably, previous production teams have chosen to keep the wonders of the TARDIS to the programme’s marginalia, having neither the budget nor, always, the backstage talent of the kind that current production designer, Michael Pickwoad displays week in, week out. But now is a good time for the programme to pick up where ‘The Doctor’s Wife’ left off, giving us the sort of story that acquires an added resonance in the 50th anniversary year.

And what a story ‘Journey to the Centre of the TARDIS’ is! Given the twists that follow late on in the episode, as the ship starts leaking time, it’s as well that the essential story, of a team of intergalactic salvage operators, is a simple one. The brothers Gregor, Tricky and Bram are a fairly obtuse bunch: singular in ambition and fairly low-key in performance too.

But just because these guys aren’t going to be joining the Doctor’s quiz team doesn’t mean they can’t do serious damage. It shouldn’t be quite as emotionally affecting as it is to see Bram start attacking the TARDIS doors with a sledgehammer and a chainsaw. Then again, it’s not just any blue box he’s attacking. It’s one with fifty years of memories inbuilt.

Lying half on its side, the TARDIS appears unusually vulnerable and disconsolate, and yet it’s telling that, as the episode proceeds, we are also quite prepared to accept her as a place of previously unknown, but suspected, horrors. The twist that the charcoal ash monsters are who they are is a fine one; but to work as well as it does, it’s dependent on us willing to entertain the possibility, as Clara does, that both the Doctor and his machine are the greater threats.

Michael Pickwoad will rightly win the plaudits here for his inventive use of studio space and set decoration. However, it would be wrong to overlook the many directorial decisions of Mat King, which serve to ramp up the tension and claustrophobia. The colour palette of the episode is striking. Dominant blues and reds in the early part of the episode segue into greens and yellows, then latterly brilliant whites. The soundscape is a mixture of slavering snarls, pulsing heartbeats and soft rock music cues.

Monsters appear blurry, kept just out of the field of vision, while familiar voices whisper in the auditory shadows, occasionally coming into sharp focus, as when the voices of Susan and Ian, alongside those of the Third and Ninth Doctors, speak of the ship’s infinite capacity.

For those of us who have tired a little of Matt Smith’s kid-in-a-candy-shop goofiness of late, he provides a Doctor as changeable and unknowable as the landscape in which he lives. He’s all clenching jaw and consonants when he appraises Clara as ‘Feisty’, becomes proud steel when announcing ‘My ship! My rules!’, then pulls the rug on his own performance with his blokey assessment of his delivery, ‘I thought I’d rushed it a bit!’

Good guys do not have zombie creatures. But they do, it turns out, have secrets in dusty old books. The Doctor may be determined to uncover the mystery of Clara, but it’s the true history of the Time War where the greatest mystery is to be found.

In an episode full of best scenes, the ones in the TARDIS Library are a particular standout. We always knew that the Doctor had a taste for English stately home chic. What’s new is the Escher-like recursiveness of the space, as well as the Hogwartsian touches: the sacred texts and bottles of Encyclopedia Gallifreya that dribble away like fine wine. As production design to reveal story goes, we’re a long way from the corridors of an old mental hospital.

For some, it’s possible that the big friendly button which fixes the plot may be a MacGuffin. But we rather feel that, because it celebrates its own MacGuffinness and is seeded so well throughout the episode, it is rather charming and neat. Yes, there is an in-your-face audacity to the conceit, but so what? This is Doctor Who.

The moment when the Doctor grasps the significance of the button is beautifully told and played. It’s the stillness of the engine room – the vacant brokenness of the space – which causes the Doctor to grieve for his ship, which causes Clara instinctively to take his hand, which causes the Doctor to notice the message written thereon. It’s a storytelling sequence of toppling dominos, and a reminder that the Doctor is at his most brilliant not when there is suspicion and enmity between him and his companion, but when the two of them are connecting. When Gregor and Tricky touch, time reasserts itself. When the Doctor and Clara touch, the narrative reasserts itself. That’s clever storytelling.

Aired at 6.30pm on Saturday 27 April on BBC One.

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