This even manages to largely avoid the persistent failing of the Hinchliffe era: half-baked endings. Partly that’s because after the steady pace of the first three episodes, this is pretty much non-stop action and peril. While Uvanov and Toos hold the bridge, the Doctor, Leela and D84 go to confront Taren Capel, and in a fairly relentless series of lashed-up bombs, laser probes and robot deactivation devices the robot revolution is defeated. It’s not the tidiest climax, and it abandons the conventions of the detective novel (which would have seen the Doctor gather the survivors in the lounge to unmask Taren Capel). However, everyone gets to play a part, Uvanov is revealed not to be the heartless manslaughterer Poul led us to believe, Toos gets to deduce that SV7 has been “turned”, and D84 becomes a hero.

Boucher’s commitment to world-building continues right through to the end, with a discussion of Grimwade Syndrome, and some musings on body language and the “uncanny valley” of androids. It’s no surprise that spin-off media keep coming back to this serial because it so richly paints a world beyond the single Sandminer we see. The unseen Kaldor City, the powerful Company, even the backstory of individual characters are all much more vivid than in, say, The Android Invasion or even Terror of the Zygons. It’s the same kind of lived-in universe that makes Star Wars so enduring. Plus, it’s executed brilliantly and wittily. In this episode alone we get the Doctor carrying Uvanov like they’re Kevin Costner and Whitney Houston.

The characterisation of the regulars is interesting. Possibly it’s Chris Boucher’s instinct that the Doctor insists on the people he helps taking some responsibility for their own salvation. After he told the Mordee their future was ‘not my problem’ in The Face of Evil, here he snaps at Uvanov that using the anti-robot bombs is ‘your problem’. However, it echoes a scene in The Seeds of Doom where the Doctor tells the Antarctic crew, ‘You must help yourselves’ and makes me wonder how much is Robert Holmes’ politics of self-reliance (reflected in his own anti-tax The Sun Makers). Leela has some great moments in this too, as you might expect, helping save the day while the Doctor is tied up, rescuing Toos (and forming a fairly compelling partnership with her – nice to see, given both actors were competing for the role of Leela), and trusting her instincts when danger looms.

Overall, I think this probably represents another new high watermark for the show. It’s not perfect (this is a robust rather than a graceful finale), however it keeps all its elements – humour and horror; SF ideas and character drama; the relationship between the regulars; references to the Doctor’s past and Time Lord powers – in balance, something the series will increasingly struggle to do in the coming years.

Next episode: The Talons of Weng-Chiang