Doctor Who The Zygon Invasion review: David Tennant's favourite shapeshifters are back in a suspenseful commentary on real-world crises

I’m rather envious that, in 1975, Radio Times’s stalwart snapper Don Smith took his son on set to meet the fourth Doctor and his monstrous new opponents. Don wasn’t even taking official Who photographs for RT that day. (None appeared in the magazine and none exist in our archive.) He was simply giving his lad a treat and took a couple of memento shots.

David Tennant often said the Zygons were his favourite childhood monsters. And I loved to loathe them when I was a child. I’ve suddenly remembered a dear old lady, Miss Belsham, who used to give me piano lessons; she’d extol Strauss and Beethoven, while I retaliated with random flashes from my Doctor Who scrapbook. She had a strong stomach but recoiled at the sight of a 1975 Zygon. “It looks like the most hideous baby,” she observed, gagging.

I suppose they do resemble a deformed embryo, spliced with seahorse DNA, smothered in calamari and dipped in salsa. They were the result of a skilful collaboration between BBC costume designer James Acheson (who later won three Oscars) and prosthetics pioneer John Friedlander (who also sculpted Davros’s mask in '75). It’s a pleasure to see the Zygons back – largely untouched – in what Steven Moffat describes as “a belter of a global thriller”.

Alien shapeshifters are always a tough sell. You either buy the idea or you don’t. And I struggle. As if by magic, they not only copy our bodies but our hair-styles, vocal patterns and, crucially, our clothes and footwear. Hey presto! Most sci-fi shows indulge in them, from Star Trek to The X-Files, and Doctor Who has offered numerous examples, some even predating the Zygons (eg Chameleons in 1967 and Axons in 1971).

Today’s Zygons no longer operate by “the old rules” of the 70s whereby the original humans had to be kept alive for the imprint to endure. Now they can “pluck loved ones from your memory and wear their faces”. It’s daft but keeps the pace up and opens up more dramatic possibilities.

The basic concept of this two-parter is Steven Moffat’s and he’s gifted it to Peter Harness, one of Doctor Who’s new great finds. Peter wrote last year’s Kill the Moon, which earned a mixed response and was greatly enjoyed by me. He adapted the bizarre Jonathan Strange & Mr Norrell for BBC1 earlier this year; but perhaps what’s more relevant to this task is that he’s the showrunner of Wallander (the British version starring Kenneth Branagh).

A key preoccupation of Henning Mankell’s Wallander detective novels (set in Sweden) was to show us the way we live now, how ethnic minorities try to rub along with a majority population; he would never demonise migrants or outsiders but humanise them as victims of circumstance, exploited by indigenous criminals. Peter Harness is steeped in all this and it informs his latest Doctor Who.

With its allusions to Isis and direct mentions of radicalisation, terrorist training camps and splinter groups, The Zygon Invasion is the closest Doctor Who has ever dared come to commenting on the woes of the world. It’s brave and may look like a toned-down Spooks or even Homeland, but perhaps its deepest roots lie in Mankell’s Baltic of the 1990s.

Again women are to the fore. Anyone criticising Moffat’s era for misogyny needs an eye test quite frankly. Apart from the Doctor, nearly all the key parts here are female (as they have been throughout this series). I like the notion of Kate Stewart as the late Brigadier’s daughter and head of Unit but, please, couldn’t someone slip Jemma Redgrave a double espresso or a vodka Red Bull? OK, she’s the Harry Pearce of this tale, but is she taking a degree in stoicism?

As Unit operative Jac, lovely Jaye Griffiths enlivens a part that is thinly drawn and has no hinterland, so that we feel for her when she’s tricked and torched. Rebecca Front is off-the-wall casting as the gung-ho Colonel Walsh but it’s good to see her in a frosty dramatic part. She has decades of comedy under her belt, was Peter Capaldi’s sparring partner in The Thick of It, and has come a long way from the “borderline shy/wild” airhead Cherysh in my favourite episode of Ab Fab.

The most interesting character is Zygood – sorry, Osgood. Ingrid Oliver is a sweetheart in the part of the Unit boffin who may or may not be a Zygon. I don’t actually care either way. I’m more intrigued to know: will we ever find out her first name? She’s appeared in three episodes since 2013 and not a sniff of a name. But that’s a Unit tradition. In the 1970s, Sergeant Benton was around for seven years and never had a first name. It was six years and 83 episodes before we discovered that the Brigadier’s name was Alistair. So, way to go, Osgood – if you live that long…

The Zygon Invasion isn’t quite the tense global thriller it’s been touted as. It pootles along with a lot of engaging set-up and a few shudders and moments of suspense. For a long while, the creepiest incident is the 12th Doctor loitering in a children’s playground chatting to two blonde Zygirls with their hair in bunches.

It doesn’t really ramp up the thrills until the final few minutes. All Unit’s bases around the world are “neutralised”. All the heroes are in various states of peril, perhaps dead. And rather fabulously Clara/Zygon fires a missile at the presidential plane with the Doctor aboard. Harness has generated an exciting multiple cliffhanger.

But me being me, what I’m wondering most is: why the hell hasn’t the snarling, tied-up Zygon effected his escape by shape-shifting into a mouse, an earwig or a canary…? He should really have one of those in a pod somewhere!

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