The Avengers in Colour. Four words that signal the most significant drop in quality in the show’s run. It starts with a downgrade of the titles. (Actually, it starts with a wonderfully suggestive sequence in which Mrs Peel fires a shot, and Steed’s champagne gushes forth; but standards drop soon after.) The new titles are posed by live action. Gone are the stylish stills; instead we get our leads wobbling as they try to hold still or make deliberate gestures. It’s worst at the end with the low lighting and the silhouettes. And, visually, it doesn’t get much better once we get in to the episode. The colour is garish, excessive, uncoordinated. Steed wears a burgundy suit. A BURGUNDY SUIT. And his bow tie is HORRIBLE. But it’s not just the muddy mix of colours; all of the bold visual sense that has been with the show right since the early episodes (fully fledged in The Frighteners) has apparently gone. It just looks like all the other highly coloured ITV shows of the 60s and 70s. Also the studio shots are terribly obvious, which must be partly to do with the differences in lighting for colour (yes, I know I complained about the studio shots in the black & white Thirteenth Hole but generally they’ve been almost imperceptible).

The Philip Levene scripted story itself is so-so. The fantastical is there in a suggestion of alien invasion – which at least several of the characters believe. (The problem is that after The Man-Eater of Surrey Green it has been established that this is a possibility). The conclusion tries to rationalise all of this – although it doesn’t make much effort to explain the motivation for the sham Venusians. A bigger problem is the laser technology in this: it’s a visible light that is capable of both bleaching and burning through thick metal. And, for good measure, it boils any nearby beer. And it bleaches hair, but not skin. It bleaches soot. It also manages to put bleached soot on a previously pristine LP. Best of all they make a loud and distinctive sound. Impressive.

Emma gets tied to a chair and threatened with a laser, Goldfinger style (I was almost supposing we’d get “Do you expect me to talk” “No Mrs Peel, I expect you to die” but in fact he does expect her to talk. Ah well.) This is Philip Locke’s last Avengers (after The Frighteners and Mandrake, both of which were superior stories).

There’s comedy Mary Poppins style chimney sweep in a top hat (Bert Smith, née Bertram Fortescue Winthrop Smythe) who gets quite poetic about astronomy. And there’s a woman called Venus Brown, but no reference to her namesake (the now tragically forgotten) Venus Smith. But the best guest appearance – and the scenes that steal the show – are from a character that will be very familiar to fans of UNIT-era Doctor Who, a Brigadier played by none other than… Jon Pertwee! (You see what I did there?) Costume aside, he’s basically playing The Doctor in this, narrating one of his adventures with UNIT.

Other new stuff: Mrs Peel’s apartment. She’s clearly moved, and it’s a bit pokey and lacks the views. And I’ll admit to being surprised by her auburn hair; whilst only ever seeing her in black and white I’d assumed it to be dark brown!

Finally we no longer get transport in the tag scenes; instead there’s some ‘witty’ follow up to the story that’s gone before. But there are two new traditions: there’s a subtitle for each episode, here: “Steed is shot fill of holes. Emma sees stars.”  And afterwards, Steed always arrives to say “Mrs Peel, We’re Needed” – here: arriving at her apartment with a card skewered on his umbrella.