Childhood is no place for children. When their mum’s away, 15-year-old Elliott and 14-year-old Maggie play a variety of games to distract Finn, their young brother. But, when it slowly emerges that perhaps their mother isn’t coming back, what will happen to the family?

Polly Stenham’s eagerly awaited follow-up to her 2007 hit, That Face, doesn’t disappoint. Once again, she shines a bright light into secret corners, and is especially observant in her account of the gender wars that occur in each family, and the different bonds that bind mother and son, and mother and daughter.

In this drama, loyalty is a key theme, and child’s play becomes a tactic in the power game between siblings in a world that mixes the imagination of Peter Pan with the viciousness of Lord of the Flies. Stenham’s distinctive voice - viscerally punky, hilariously dirty and thrillingly fierce in its emotions - comes across loud and clear in this absorbing, witty and fully-imagined show.

Tusk Tusk is brilliantly directed by Jeremy Herrin, whose young cast add a touch of real playfulness, naivety and vulnerability to Stenham’s characters. Making their professional debut, Toby Regbo, a steadfast Elliott, and Bel Powley, a needy Maggie, are both excellent, while Finn Bennett, who shares the role of Finn with Austin Moulton, convincingly mixes fragility and boisterousness.

Even the smaller parts feel just right - Georgia Groome as a working-class teen picked up by Elliott, plus Caroline Harker and Tom Beard, who represent the adult world. On designer Robert Innes Hopkins’ kitchen set, so realistic you can watch the food decay on the unwashed dishes, this mix of urban fairytale and psychological thriller sets the pulse racing. Surely this is the most enjoyable piece of new writing on the London stage.