Back after a five-week Christmas break for what could very much be called “Season 14B”, there’s a shift in tone for this serial. It’s not just that Sarah Jane, our last link to the Barry Letts era, has gone, it’s something more fundamental than that. When he arrived, Tom was the weird, unpredictable, alien Doctor grounded by Sarah Jane, who has to remind him of the little niceties when he’s moodily musing about eternity. Now, he’s the one talking directly to the audience (though he stops short of wishing a happy new year to all of us at home), our familiar touchstone and voice of moral authority, while Sarah Jane’s replacement is a savage woman from the future who goes round killing people with crossbows and poisonous thorns.

Louise Jameson is immediately impressive: her commitment to the character of Leela is obvious; it’s there not only in her slightly formal delivery, but in her movement, and her reactions: both childlike, when she meets the Doctor and mistake him for the Evil One, and sharply perceptive. She makes what could have been a bit of titillation for the dads into a credible, dangerous person. She’s surrounded by some pretty strong actors in the Tribe of the Sevateem and acts them all off the screen.

But it’s not just Jameson who arrives in The Face of Evil. It’s a proper changing of the guard: the first story for writer Chris Boucher and director Pennant Roberts, both of whom went on to be key members of the Blake’s 7 production team. Maybe that’s why this feels like such a shift: suddenly the show is sliding into that last-1970s/early-1980s BBC sci-fi style. Maybe that’s why the alien jungle is suddenly not like the colourful and weird sets of Planet of the Daleks or Planet of Evil, but instead looks starker and bleaker.

Sad fact: as of today, this is the earliest Doctor Who story where the producer, writer and regular cast are all still with us.

Next episode: The Face of Evil – Part Two