Tickets for Elling were sold out before opening night, probably because John Simm, the star of Life on Mars, plays the title role. But terrific as Simm is, he’s only one reason to catch this quirky comedy.

Originally a Norwegian novel by Ingvar Ambjørnsen, it’s now presented in Simon Bent’s English-language version, directed by Paul Miller. With riotous humour and enormous charm, it lightly addresses the relationship between life and art, suggesting that reality is what we make it.

The fastidious, neurotic mother’s boy Elling and the “chick”-fixated, hulking 40-year-old virgin Kjell Bjarne are roommates in a psychiatric institution. They strike up a friendship – despite the interference of the formidable Nurse Gunn, who discovers, in Elling’s secret notebook, all manner of waspishly witty, insulting scribblings about Kjell Bjarne and herself.

If Elling can turn a wounding, well-observed phrase, he can also spin a yarn, and he diverts his friend with exotic tales whose implausibility is, as Kjell Bjarne happily points out, no barrier to their capacity to entertain. Under the eye of Frank, a good-natured social worker, the pair are installed in an Oslo flat in the hope that they will reintegrate into society. The everyday business of looking after themselves poses a challenge; but, prompted by outlandish encounters with two strangers, they inch closer, albeit in eccentric fashion, to happiness.

It’s an urban fairytale with a sprinkling of religious symbolism. The blonde, pregnant neighbour who tumbles drunkenly down the stairs on Christmas Eve, landing on their doorstep, is to Kjell Bjarne a fallen angel. Elling sees his dead mother, whose all-consuming love has stymied him, as a pure Madonna.

There’s something otherworldly, too, about the benevolent silver-haired gentleman who pops up in unlikely places and fuels Elling’s ambition to become a poet. And, with gentle irony, it’s only as Elling and Kjell Bjarne’s existence grows more chaotic that they become “normal”.

The performances are a joy. Simm’s Elling is a twitching, acid-tongued, buttoned-up model of prissy precision, Adrian Bower’s Kjell Bjarne loping, cuddly and malodorous, exactly the soulful-eyed orang-utan that Elling labels him. Watching them first resist, then connect with, a world that proves remarkably compassionate and accommodating is moving and very, very funny. Thoroughly life-affirming.

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