Jemma Kennedy’s play about the business (in every sense) of human fertility is smart, funny and complex. And the closer it gets to saying what it seems to want to say, the more of a mess it becomes.

Harry Enfield’s second ever appearance in a stage play is much more assured than his first, some 18 months ago. He’s still a little deliberate with the hand gestures, and still noticeably “doing” a character, but since he plays not only the director of an IVF clinic about to be floated on the stock market but also Karl Marx (with a press-night moustache malfunction), this is understandable. He fits well in Laurie Sansom’s slick, sardonic production with its multiple video screens and bizarre pre-show music: plinky-plonk, synthetic-chiming arrangements of songs from Run-DMC’s “Walk This Way” to Radiohead’s “No Surprises”.

Several plot strands interweave. The broker handling the clinic’s flotation wants a child of her own, fathered by her lodger whom she’s loved since their youth but who has since come out as gay; a couple using the clinic fall apart when the husband cannot share the wife’s fervent commitment to the process; they separate, she seeks a sperm donor... and finds the gay lodger is willing... And that’s not even mentioning the husband’s social-services client or the several fantasy sequences featuring not only Marx but Biblical figures Abraham and Sarah and even – I kid you not – Susan Sontag.

A lot of potential, you might infer, for failing to tie things together coherently, and you’d be right. The climactic scene of mutual truth-telling seems, paradoxically, a little boring: so many different things mean so much to so many characters, yet we never invest emotionally with them. Kennedy seems to know she can’t get away with it all, so writes a parodic, happy-ever-after sentimental ending, then deflates it... and inflates a minor-key but no less sentimental ending which she appears to offer in all seriousness. It even includes a closing ballad (the lodger happens to be a music teacher, and of course Arthur Darvill has the musical chops to carry off the piano/vocal work). The journey is exhilarating, but the destination, such as it is, is banal.

Written for the Financial Times.