You’ve got to admire the creative commitment displayed by Broton, Warlord of the Zygons (John Woodnutt). He’s disguised himself as the patrician Duke of Forgill – he’s got the coat, the hat and the cold, aloof exterior of the minor aristocrat down pat. He flaunts his performance at every opportunity, even though it brings unwelcome attention to his real agenda, which is to destroy oil rigs with his fearsome, half-mechanical Skarasan. Skarasan being a Zygonian word meaning ‘sea cow’.

Broton must simply love the theatrics of it. How else to explain why he drives into town (picking up three oddly dressed hitchhikers on the way) specifically to heckle oil man Mr Huckle (Tony Sibbald) about his employees trespassing on his appropriated estate, deliberately mangling the poor bloke’s name to press home his disdain. A few oiks skyving off on the moors for a quick ciggie can’t pose much of a threat to the warlord of an advanced technological race.

But Broton really throws himself into the part anyway. “If my ghillie catches them on my land again, they’ll be shot,” he burrs menacingly. Surprisingly, no one present – not the Doctor (a gruff Tom Baker), the Brigadier (an amiable Nicholas Courtney) nor Mr Huxtable himself – mentions that is a fairly drastic step up from a stern warning and a markdown at their next performance review.

Terror of the Zygons is full of these odd moments. Not ineffective, mind. Just the opposite. They are usually well acted, stylishly directed vignettes. But they’re just strange enough to jolt you out of the story for a moment. Either that, or they’re completely superfluous to the plot.

For example, take hard hitting journalist Sarah Jane Smith (a stylish Elisabeth Sladen) and her interview with bagpipe-playing, sooth-saying Angus McRanald (Angus Lennie). With wide eyes and hushed tones, he tells her the sort of spooky stories that teenage girls use to freak each other out at sleepover parties. Of the man from the Black Isle who went missing on the Moor in 1922. And of the Jamieson boys of 1870: “They went out cutting peat and the mist came down. Donald just disappeared. They found the older brother, Robert, two days later, wandering about, off his head. His eyes, his eyes were terrible to see.” Look, it’s lovely stuff, but unless we find out later in the story that the disappearances were part of the Zygons’ nefarious plans (and we don’t) it’s pleasantly creepy scene setting, but of no plot value.

Then there’s a series of land rover related coincidences, which kick off with Broton driving past the Doctor, Sarah and Harry (a dependable Ian Marter) at exactly the right time to pick them up (why not just have them land in the town itself?). Not long after, Harry is driving a land rover down a random road at exactly the right time to find an injured oil rig worker and get shot himself (Broton wasn’t bluffing, as it turns out). And not long after that, the Doctor is driving a land rover, trying to draw off the aforementioned hungry sea cow, when it mysteriously breaks down. Inconvenient for the Doctor who then has try to outrun the beast, but handy for a cliffhanger.

Back to the Zygons’ penchant for dramatics for a moment. Not all of them are as skilled as Broton. He must have gone to RADA, given his commitment to a role, but the others have clearly graduated from the diploma of performing arts at Wollongong TAFE, so clearly do they signpost their evil intentions. The one masquerading as Sister Lamont (Lillias Walker) is giving a Botcherby worthy performance in sinister, which is surely exactly what you don’t want if you’re trying to hide out in a local hospital. (And by the way, why impersonate Sister Lamont? Is to finish off all those poor injured oil rig workers?) The Zygon who copies jolly, avuncular Harry gets his performance spectacularly wrong, making him a study in cold, sneering disdain. Sarah sees through him immediately, which was surely not the intention.

Like an actor in an hot, uncomfortable rubber costume, the Zygons must hate dressing up as humans, which might account for their inconsistent performances. “I loathe this abomination of a body,” the Lamont Zygon says at one stage, managing to keep a straight face. To be fair, those Zygon bodies are a terrific design, the bloated heads giving the impression of big orange embryoes (zygotes, I suppose). The new series Zygons seem to have done away with that association, which is probably wise. When Broton reveals that they feed off the milk of the rubbery Skarasan, the immediate mental image of a half a dozen Zygons suckling at the numerous teats of the puppety thing is another one of those story jolting moments. New Who can do without that.

Inside the Zygons’ spaceship, they’ve clearly gone for design over practicality. On the outside, it just looks like your standard tin box affair, but inside it looks like some something that’s been growing in the back of your fridge has got ideas above its station, and sprouted protuberances everywhere. The Zygons operate it by gently squeezing and fondling the various spongy bits which emerge, and it’s all very suspect in a masseur-who’s-crossed-the-line kind of way.

The Doctor, taken prisoner aboard the springy craft, is unfazed. He can instantly identify a fire sensor, a vacuum mechanism and a self destruct button even though they all look like indistinguishable orange growths. He’s that kind of guy. Anyway, his meddling forces the spaceship to land in a disused quarry (which for once is not code for an alien planet), which proves to be a good place to blow the whole thing up.

Except, in one of those annoying narrative dog legs, the story’s not quite over yet. Broton and the Skarasan are still on the loose. Earlier, Sarah and Harry, realising they had nothing in that episode to do, decided to go and rifle through Forgill castle, looking for clues to Broton’s plans. There Sarah discovered:

SARAH: The Duke is Chieftain of the Antlers Association, Trustee of the Golden Haggis Lucky Dip, whatever that might be, and President of the Scottish Energy Commission.

But then our investigative duo decided this was a waste of time and went back to the main plot. Once we get to the quarry, our heroes start to put all this together. Broton, it transpires, wants to go to an energy conference in London.

BRIGADIER: Yes, but he’d need a pass to get in. The security’s very tight.

SARAH: But he’ll have a pass. The Duke, the real Duke, is President of the Scottish Energy Commission.

DUKE: That’s right. I am!

Nice one Sarah. Except because the Duke is actually present in this scene, he could have told everyone that himself. Meaning that whole little detour of yours to the castle was meaningless padding. Still, I suppose it beats listening to more ghost stories with wee Angus McRanald.

Personally, I wish Broton would have staged his final endgame at the Golden Haggis Lucky Dip. That sounds much more fun than an energy conference which consists of a cellar, a corridor and a balcony, which cries ‘we spent all the design budget on the Zygon pizzamobile’.

It all ends with Broton dying with true Olivier-style gusto and the Skarasan wobbling unconvincingly on a CSO backdrop before heading back to Loch Ness. Weirdly, our heroes all follow suit, catching the train from London. Wouldn’t it have been easier to just put the TARDIS on the back of a land rover and have it driven it to them? No wait, on second thought, we know how unreliable those things are. You wouldn’t risk it.

LINK TO The Empty Child/The Doctor Dances: both feature Americans, or at least characters with American accents.

NEXT TIME: We count how many beans make five with Mawdryn Undead.