The conclusion to the story is largely perfunctory, which only adds to the sense that beyond giving Troughton the opportunity to play the Great Dictator, Whitaker didn’t really have much idea what to do with this. The introduction of the secret bunker filled with middle class people never gels with the rest of the less absurd plot elements; Giles Kent’s unmasking is a bit clumsy, and rather than providing any sort of satisfactory denouement, Whitaker just blows everything up.

Charitably, you could argue that he’s just borrowing tropes from the Bond movies: the ‘Double-Zero-One’ is an obvious wink in that direction. But the most Bondian thing about all of this is from a film that won’t be made for another six years: Salamander stalking Kent through the tunnels like Scaramanga hunting a victim through his fun house. This sequence is short but effective, and there are other nice touches, like Benik’s cowardly attempt at escape quickly followed by his demand for the kind of fair trial he denied his victims. Astrid’s arrival in the bunker, and its inhabitants’ terrified reaction, is convincing. And the final fight between the Doctor and Salamander, though brief, fulfils the basic need in an evil double story for the two to meet. His fate – sucked into the time vortex – is a fittingly grandiose exit for a larger-than-life character.

The main theme of the story: that those who use or threaten force to bend others to their will, whatever the virtue of their cause, must be fought is re-emphasised in the Doctor’s rebuke to Kent: ‘Any man who resorts to murder as easily and as rapidly as you must be suspect.’ It’s a timeless message, but probably didn’t need 150 minutes to make. It’s a joy to have the serial back in the archives, of course, but it’s hardly a classic. The regulars spend most of the story as passive observers (Jamie and Victoria aren’t even in the fourth episode, and the Doctor spends almost the first five episodes in lounges, refusing to get involved). It takes someone of Troughton’s abilities to hold together what’s a fairly half-witted story.

Next episode: The Web of Fear