Having worked out what Scaroth is up to, this final episode sees the Doctor comprehensively dismantle both the Count’s carefully-constructed façade, and Scaroth’s 400 million year plan to alter the course of time. Tom Baker plays this like Poirot brilliantly foiling the villain: the tomfoolery is largely put aside and instead the Doctor shows off his keen insight and wisdom as he unpicks the Countess’ ‘discretion and charm’ and in a few moments playing on her doubts about her husband to the point where she’s ready to pull a gun on the Count. Then, for desserts, he confronts Scaroth himself.

Again, this is a dense, wordy, witty script, and one that satisfactorily ties together all the hints and references in the last three episodes. The show’s got much better at its endings since Robert Holmes left: Adams is much better at pulling the ribbons together and wrapping up the story in a neat bow. For anyone in the audience wondering how the Count has managed to fool the Countess for so many years, this oh-so-discreetly addresses the elephant in the room:

THE DOCTOR: You’d like to see yourself as his consort. But what’s he doing in the cellar?
COUNTESS: Tinkering. Every man must have his hobby
THE DOCTOR: Man? Are you sure of that?

The look that passes over the Countess’ face as the Doctor questions her husband’s manhood says they both know she’s no consort. Of course, she’s not expecting the truth to be that he’s an alien warlord, but the point stands (or doesn’t, if you get my meaning).

And I absolutely love how this sham marriage is given equal weight to the cosmic nature of Scaroth’s villainy. He may have manipulated humankind since the Pyramids, but that’s made tangible at a relatable scale by the way he’s played the Countess for years. It’s important that Scaroth gets to reveal the truth to the Countess and kill her with contempt, because it illustrates exactly what the human race means to him: ‘It has not been difficult keeping secrets from you my dear.’

This is packed with similar moments: ‘Is no-one interested in history?’ yells the Doctor as the human race goes about its mundane business. The birth of life on Earth in a pond of slime, no glorious spark from God’s finger, but the by-product of an monster’s accident is astonishing. David Attenborough’s landmark Life on Earth aired in early 1979, and this reminds me, oddly, of its mix of awe and matter-of-factness. The John Cleese and Eleanor Bron cameo is inessential but illustrates the idea of pseuds more interested in looking for clever meanings than appreciating whether something looks good or not (mea culpa). It’s also wonderfully self-reflexive: since it has no call to be there, the art lies in the fact that it is there.

Really, the only thing that feels too weak to have made the final cut is Romana suddenly and conveniently remembering that she’s built a two-minute window into the stabiliser, just to give Scaroth an exit that sees him catapulted back to the cellar and destruction. But that’s a tiny flaw that’s more niggling than it should be because everything else is so perfect. The final musical sting sounds like it’s going to go into the Miss Marple theme.

Next episode: The Creature from the Pit