Again, this is mostly exposition rather than action. Again, when the exposition is done this wittily and this well, it barely matters (although I still wonder what the eight-year-olds in the audience made of it). If any of the main performances were sub-par, this wouldn’t work as well. But Julian Glover is excellent, doing his best Olivier Richard III as he confronts the Doctor in 1505; being the perfect host to Romana in 1979. Like Kevin Stoney’s classic villains, Scaroth is willing to play along with the jokes providing he’s getting what he wants, but kills without hesitation when the joke wears thin. Tancredi’s, ‘You can write, can’t you?’ and Scarlioni’s twinkling smile as the Professor is aged to death are brilliantly horrid.

The Pertwee references in the last episode are fitting, given this reveals Scaroth to be another baddie in the spirit of Azal, guiding and manipulating the entire human species: he’s ‘brought up a whole race from nothing to save his own race.’ The ancient astronaut reveal: that Tancredi and Scarlioni are merely fragments of an alien splintered across the history of Earth, guiding humankind towards its destiny, is Image of the Fendahl stuff: a pastiche, at the end of the decade, of the quintessential Quatermass and the Pit plot that the show’s been mining through the Seventies.

The big plot stuff freshly reworks familiar concerns; the details are beautifully observed. Peter Halliday’s soldier explains, for anyone in the audience vexed by it, how Scaroth can get away with being so weird: ‘When you work for the Borgias you believe anything.’ Money and power can induce most people, in any century, to turn a blind eye. Duggan remains a bull in a china shop, smashing his way into restaurants and wine bottles equally, but he’s right: he does get results. Romana keeping her hands up as the Count invites her to take a seat is cute, and it’s good to see a companion valued for her intellect rather than as a hostage. Wonderful.

Next episode: City of Death – Part Four