The Secret Diary of Adrian Mole Aged 13 3/4 (Leicester Curve)

What’s Adrian Mole without his diary? A fairly ordinary lad from Leicester, it turns out, whose parents are in the process of splitting up.

Sue Townsend’s much-loved account of adolescence, written as the day-by-day jottings of a tortured, pimpled pubescent, is one of those books, like Huckleberry Finn and Catcher in the Rye, that absolutely depends on its narrator’s voice. She lets you see the world through teenage eyes, so that spots loom large as planets and Pandora – the love of his life – is everything and everywhere. We see his mother’s absence, once she’s eloped with Mr Lucas next door, and his father’s resultant depression as he does: incomprehensible and excruciating.

Jake Brunger and Pippa Cleary‘s musical can’t really do that. Occasionally, Adrian comes downstage to address us directly, explaining some convoluted theory or pining over Pandora, but mostly he slots into his own story. Instead of his misinterpretations, coloured by naivety and hormones, we see events as they really happen, with Adrian merely looking on bemused. If ever an adaptation cried out for formal invention, it’s this. Instead, we get Townsend’s plot – such as it is – squeezed into a fairly conventional shape and in the process it becomes, more or less, a touching dramatization of a divorce.

Think of Adrian Mole, though, and you don’t think of marital breakdown. You think of the agonies – and they are agonies – of adolescence. The diary format turns time into something felt: banal routines on repeat and slow, seismic shifts. ("Nothing happened at all today, apart from a hail storm around six o’clock"). Musicals, meanwhile, function episodically, with individual events dispatched in single songs. Here Adrian doesn’t live with tonsillitis, he contracts it and recovers. He doesn’t long and long and long for Pandora, he falls for her then, soon after, she falls for him. This is A. Mole diluted, not A. Mole distilled.

Which isn’t to say that it’s not a decent musical – albeit well short of Matilda or Billy Elliot. There are flashes of brilliance and, even if Luke Sheppard‘s production feels like an extended kids television sketch, Brunger’s book brings out the story’s shape, so that as Adrian loses Pandora to his best friend Nigel, his dad’s sat boozing and broken-hearted over a runaway wife. Cleary’s music is best in such touching moments: "Perfect Mother", "My Lost Love" and "I Miss Our Life" are all delicate little tear-jerkers, but the score needs one or two more rousing ensemble numbers to really take off.

Brunger’s mirroring adolescents and adults also instils a strong feminist streak and you see Townsend pushing against patriarchy in focussing on Mrs T and Lady Di, showing the way women are objectified and enslaved in relationships. The byproduct is that, by showing Adrian becoming a man, following his father’s footsteps, you lose the sense of puberty as its own state of being, as a kind of limbo existence.

Still, Joel Fossard-Jones, one of four Adrians, is smartly cast: his genuine gawkiness adds a charm of its own, even if he’s not quite dorky enough. (Another product, perhaps, of perspective: no overwhelming insecurities). Imogen Gurney is pure precocity as Pandora, forever presenting like some kind of show pony, and, as Adrian’s parents, Kirsty Hoiles and Neil Ditt are entirely relatable. Cameron Blakely and Amy Booth-Steel provide plenty of characterful support as assorted adults, all of them slightly inexplicable to our Mole. If only he were our man on the inside.

The Secret Diary of Adrian Mole aged 13 3/4 runs at the Curve Theatre, Leicester until 4 April

Read our interview with director Luke Sheppard here