‘Doctor who? Have you never wondered where he came from, who he is?’ Lady Peinforte knows the Doctor’s secrets, of Gallifrey and the old time. So, a mysterious time-travelling woman of questionable morals who knows the Doctor, and likes to pick up handsome young men as she searches for ancient, hidden artefacts: Peinforte is clearly the final incarnation of River Song. Her threats are empty, in the end, because (implausibly but brilliantly) the CyberLeader isn’t interested, and so it’s just a shaggy-dog tale. The Doctor’s dark past doesn’t matter, it is irrelevant to who the character is.

Which is as apt a punchline to this strand of storytelling as any. The best thing about the “Cartmel masterplan” – an attempt to “reintroduce mystery” into the character of the Doctor – is that the show ended before it could be paid off, leaving nothing more than a few dark hints, mostly in this story and Remembrance of the Daleks. Because the problem with introducing mysteries is that the audience ultimately demand the answer, and so the mystery stops being a mystery and it becomes a neverending cycle of increasingly implausible secrets behind secrets behind secrets. For anyone who was invested, the answer was ultimately revealed in the 1997 novel Lungbarrow, which posits that the Doctor has inherited the memories of a different Time Lord called the Other, a contemporary of Rassilon and Omega, and whose past lives include the Morbius faces. By 1997, though, a new secret (the Doctor is half-human!) had been introduced. And so it goes on, as if any of these revelations make any difference to a character that has been pretty unchanged – cosmetics aside – since 1964.

I think this is largely very good. The Nemesis is effectively eerie, rising like a ghost from Peinforte’s tomb and floating through the warehouse where the meteor is concealed. It’s one of the uncanniest Doctor Who monsters. A creeped-out Ace speaks to it, and it reveals it can change its appearance: ‘I have had others which would horrify you. I shall have those again.’ Only the Doctor can command it, and, rather chillingly, he still has a need of it because ‘things are still imperfect.’

Besides Nemesis, the most effective elements are the Doctor and Ace. Their little dance around a squad of Cybermen to get to the Nemesis could have been slicker, but even as staged works. Ace’s battle with the Cybermen isn’t very believable (catapulted gold coins would just bounce off Cyberman armour), but it’s well shot, with some good handheld camera work on the gantry high above the warehouse floor, and a great effect of a burning Cyberman plunging to its death. Best of all, they exude a genuinely warm relationship: Ace admits she’s scared and the Doctor pauses to apologise: ‘I’m sorry. Forgive me. Why don’t you go back to the Tardis? You’ll be safe there, whatever happens.’ Apparently, due to the production challenges on The Greatest Show in the Galaxy, McCoy and Aldred had limited rehearsal time for both this and The Happiness Patrol, and the fact that isn’t more obvious is to their credit.

The villains are less effective. Arguably the Cybermen could have been any old monster – their irrefutable logic and USP are very much not on display – but that misses the point that it’s the anniversary story and they come with a degree of audience recognition that means the show doesn’t have to spend ages establishing them. You can say the same for De Flores – he’s a Nazi in South America, the audience can fill in the gaps without lots of explanation. Peinforte needs the most explanation – and gets it: the method of the exposition (a car journey with Dolores Gray) feels like it’s JNT wish-fulfilment, like Stubby Kaye’s appearance in Delta and the Bannermen, but it’s quirky, quotable and doesn’t wreck the flow of the story.

Apart from a messy middle episode, I think Silver Nemesis works very well, full of action, humour and spectacle. The new series owes more than a small debt to the approaches Andrew Cartmel and Kevin Clarke thrashed out, and it’s not like RTD didn’t have random celebrities popping up for the special episodes. Another qualified success, then. That’s three out of three. This is shaping up to be one of the best series ever.

Next episode: The Greatest Show in the Galaxy