Like Pinter’s Betrayal, Peter Nichols’s 1981 play about marital infidelity turns theatrical convention on its head. Pinter’s work (written in 1978) tells his story in reverse while the big idea in Nichols’s play hinges on married couple Eleanor and James (Zoe Wanamaker and Owen Teale) sharing the stage with their alter egos (Samantha Bond and Oliver Cotton).

It’s a terribly clever device that allows the innermost thoughts of choral musician Eleanor and art restorer James to be subtly revealed. It also serves as a telling metaphor for the double life that adulterers necessarily have to lead. The result is highly entertaining complexity as layers of meaning behind even the most simple exchanges are revealed.

So when middle-aged James is asked by his young lover Kate why they shouldn’t have an affair, his public self (Teale) continues the small talk while his inner self (Cotton) runs through the list — love, affection, habit, cowardice, fear. It’s this syncopated stream of dialogue that elevates Passion Play above so many other adultery dramas.

But it’s an idea and plot that eventually runs out of steam. And unlike Pinter’s play, Nichols’s is almost fatally dated. James’s lover Kate (Annabel Scholey) is a thinly drawn femme fatale who specialises in hooking 50-something married men. She doesn’t have the complexity to warrant an alter ego of her own — probably a good thing considering that we would end up with six actors playing three characters. But, in the second act, the plot, which hinges on the discovery of a love letter, thins seriously.

Eleanor has indulged in a little philandering of her own, but essentially she is the hard-done-by wife who has the breakdown, sees the psychiatrist and takes the overdose of sleeping pills. But because by now we have given up caring whether the marriage survives, David Leveaux’s sexy, sometimes steamy production loses drive and tension.

As you would expect with a cast this strong, the play is well-acted. Wanamaker is an expert at revealing suppressed emotional wounds. And Samantha Bond very subtly modulates her performance in a way that mirrors Wanamaker’s both physically and vocally.

But while the genius of Nichols’s big idea remains, there is a lot here that feels as old as the play. Gender politics partly defined by a mistress unencumbered by the conventions of bourgeois and boring marriages (as Kate would see it) must have once felt awfully on the button in a post-feminist kind of way. Now it feels rather like one man’s old-fashioned view of humanity.