If we can credit the Cottesloe programme, we soon won’t have to trek to outlandish subsections of Utah to find households like the one on show in Matt Charman’s Five Wives of Maurice Pinder. Polyamorism, as it’s called by sexual anthropologists, may become rife in overpriced terrace houses in respectable Lewisham. And the polyamorist-in-chief may be neither a Mormon patriarch nor the sort of mad-eyed predator who inveigles vulnerable women into cultish seraglios but the likes of the title character, a plain-spoken, laid-back Cockney with his own scaffolding business.

Forgive me if I’m somewhat sceptical. Larry Lamb’s Maurice is a bit too good to be true or, as a feminist might say, too much the sympathetically handled fantasy of a wishful male chauvinist. Though he lays down the law about this or that, for instance demanding that squash and not alcohol is served at communal meals, he’s a large-hearted idealist who serially marries women who arouse his compassion and affection, divorcing their predecessors while keeping them both in his bed and in what he calls his “family”.

Well, Darwinian evolution could one day bring us to this, perhaps with some of the problems Maurice encounters. He may be a pretty sentimental creation but his author does acknowledge that not all his wives are wholly content with their lot. Clare Holman’s Fay takes to drink, goes out to bars and picks up stray men. Martina Laird’s Lydia vamooses with her and Maurice’s child. And Sorcha Cusack’s Esther, the senior spouse, makes it clear that she would never have tolerated polyamorism if she had had children.

Charman avoids prurient sensationalism. Rather, he suggests that this extended family is only marginally more peculiar and superficially less normal than your average Mr and Mrs Jones of SE13. A night beneath the boss man’s sheets seems to be a periodic requirement and even a chore, like washing-up. But the play has its longueurs and its implausibilities, prime among them the regular appearance of Steve John Shepherd’s Jason, who is one of Fay’s pickups and, it turns out, a local planning officer who expresses his disapproval of polyamorism by objecting to the highly symbolic extension that Maurice is building to house his expanding family.

He’s a bit of a caricature, as is Maurice’s fifth wife, Tessa Peake-Jones’s Irene, who bustles officiously about like some erotically overcharged Mrs Tiggy-Winkle. Indeed, the only character I found fully plausible was Fay’s son, Vincent, in Adam Gillen’s excellent performance an earnest nerd floundering awkwardly from bleating adolescence into twitchy adulthood. But perhaps I didn’t believe because I didn’t want to believe. Polyamorism is, after all, quite a threat both to one-man, one-woman marriage and to the nation’s gender balance. Imagine the number of spare blokes enviously eyeing the alpha males with battalions of sexpots in tow!

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