Cunk on Britain, in which history is told at us by dumb people, has been done before, of course - among others, Daisy Donovan and Ali G played the faux-naif ingenue, targeting talking-head experts with wildly varying levels of malice. And done before, anciently before, with Sellar and Yeatman's 1066 and All That, published in 1930 to frankly bemused shouts of weeping, gleeful mirth from all England's minor public schools.

But Diane Morgan, who has proved she's hardly a one-trick pony with her winningly cynical foil to Anna Maxwell Martin in Motherland, is the best yet. Not sure whether even her supreme deadpan can sustain all the expert interviewees - at some point even Diane's got to crack up - but many lines just zinged. Of the Bayeux Tapestry: "Like a Game of Thrones season finale drawn by an eight-year-old boy." Or: "It's just like being there, but in wool."

TV review, Cunk on Britain (BBC2)

A brilliant puncturing of television histories.

Philomena Cunk, the breath-takingly dim-witted arts and history presenter, ought to do a series on classical music, when she's finished her moronic survey of our island race, in Cunk On Britain (BBC2). That might take some time, since she began with the Big Bang, in an account that promises to travel 'from ancient man to Ed Sheeran'.

Cunk, played with a face as cold and immobile as a side of mutton by Motherland actress Diane Morgan, is a send-up of every self-regarding TV personality who ever recited a script while standing on a windswept cliff-edge and gazing portentiously at the horizon.

'She's like an idiot twin sister,' says Morgan. 'Occasionally she'll get things so right you think maybe she isn't an idiot. Maybe she's a genius.'

The TV in-jokes wear a bit thin. But her malapropisms are hilarious: when she talks about the king of the dinosaurs, 'T'yrannical sawdust rex', or the 'Baywatch tapestry', she's in the great comic tradition of Joyce Grenfell and Dame Edna.

The professors and historians facing her pea-brained questions evidently knew what to expect, and played along. Ronald Hutton and Neil Oliver were trying not to giggle -- but full marks to the lady at the National Archives who talked to Cunk like a weary primary schoolteacher.

No, she explained patiently, the Domesday Book isn't cursed. Perhaps they're used to daft questions at the National Archives.

Diane Morgan's deadpan ignoramus tackles the big questions in this series, starting with the big bang and stumbling blindly forward. Along the way, she takes a hatchet to the striding-and-talking tropes of the BBC factual department and baits experts with bewildering displays of idiocy ("Why did stone age people bury all their stuff underground?" she asks one baffled archaeologist). A corrective to self-important historical docs or a decent but limited joke stretched well beyond breaking point? Cunk on Britain is probably a bit of both.

Cunk on Britain preview

The only thing that doesn't quite come off are the spoof interviews don't quite come off, as experts have wised up since the day of Ali G and now seem in on the joke, matching Cunk awkward silence for awkward silence.

Diane Morgan interview

Actor and comedian Diane Morgan discusses her brilliant BBC alter ego ahead of new BBC series Cunk on Britain.

TV review: Cunk On Britain, BBC2

The dimwits are taking over. Philomena Cunk, alias Diane Morgan, finally gets a whole series in which she has the chance to look at the entire history of Britain, interview various experts and, while she is at it, get things hopelessly, hilariously wrong.

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