Polly Stenham’s first play, That Face, was a deliriously funny black comedy about a monstrously irresponsible mother and her long-suffering children. It won universal acclaim and is currently being turned into a film. Can she repeat the success, is she a permanent addition to the scene, or will she suffer from that difficult second album/novel/play syndrome? You have around about 25 or 30 years to write your first (actually Stenham did it in 19), but then only another year or so for the second.

For the first 30 minutes or so of Tusk Tusk, things certainly seem a little underpowered, and there is markedly less enjoyably nervous laughter than there was in That Face. And, once again, you have a very similar theme of maternal irresponsibility and neglected children, the great difference here being that the mother in question is absent throughout the play.

There are three children alone in a London flat: Eliot, only eight days away from his 16th birthday, Maggie, fourteen, and Finn, 7. They squabble and fight, sleep a lot, eat terrible food, let the flat slowly decay into a pigsty around them, and grow more and more unhappy. A perfect setup for a prurient Channel 4 fly-on-the-wall documentary, really. And a perfect lesson in how adolescents, even those on the cusp of nominal adulthood, are still, in many ways, children; and though it’s best not to tell them, still need looking after by a genuine adult or two.

And therein lies the problem. The children’s father died of cancer a few years ago, and their mother is mysteriously missing. She’s gone Awol before, but not for this long. But she will ring them, soon. They know she will. It’s just a matter of time. Then it will be all right.

It’s from this simple story line that Polly Stenham builds such terrific dramatic tension and unbearable poignancy. Tusk Tusk depends upon one of the most universal, perhaps the most universal primal emotion of all, more so even than love or hate: the child’s fear of losing its mother. We’ve all been there, because we’ve all been children.

The three are additionally trapped, as we gradually learn, by the fact that if they ask for any outside help, or anyone else learns of their situation, they will be split up. They are already on the “at risk” register, thanks to their mother. For the teenagers especially, it’s the thought of being split from little Finn that is unbearable. For all the squabbling and adolescent tantrums, it’s love that is keeping them together. This is even more affecting when you figure out, though it’s never explicitly stated, that Finn might well only be their half-brother, their mother’s morals being what they are, and most certainly soluble in alcohol. This leaves the two teenagers in loco parentis, which is no place for teenagers to be. They have their hands quite full enough just being teenagers.

Stenham is brilliantly served by the three young actors, each looking exactly the age they are supposed to. Toby Regbo is a jumpy, lanky, charismatic Eliot, becoming more and more tyrannical as the chaos grows around him. Inevitably, one thinks of the over quoted Larkin lines about your mum and dad, and how “Man hands on misery to man/It deepens like a coastal shelf…” Already in the 15- year-old boy, you can see a future of foul temper, cruelty, self-indulgence, drunkenness and some very irresponsible fathering habits. Bel Powley as Maggie has a terrifically glum expression and yet manages to be very funny at the same time, not least when disgusted at her brother trying to bring home a girl. And Finn Bennett as Finn himself is so utterly relaxed and natural in the role that you’re quite unaware he’s acting. There is a traumatic moment when he falls off a box and hits his head badly, when his screams are almost enough to make you want to step up on stage and intervene with some cotton wool and TCP. Full credit to the director, Jeremy Herrin, for getting so much out of his cast.

There are some wonderful plot twists towards the end, and the tension, the sense of the children’s hopeless longing, never lets up. One or two touches here are less than satisfying: for instance, the attribution of ultimate blame to a certain posh Rollo. But it’s still a blisteringly good and emotionally powerful piece.

The great task now will be how to transfer it from the intimate Royal Court Jerwood space to the bigger venue it most certainly deserves, without losing its harrowing power and close-up punch. Tusk Tusk was one of the most keenly awaited second plays this year, and I’m delighted to report that it’s so good. As a talent, Stenham is most definitely here to stay.

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