Review: The Diary of a Teenage Girl (Southwark Playhouse)

Based on a graphic novel (graphic in more ways than one) by Phoebe Gloeckner, Marielle Heller's play is an intriguing, ambiguous and quietly shocking piece of drama.

Set in 1970s San Francisco – think underage Tales Of The City, initially at least: all spliffs, Quaaludes and aching loins – the story is told from the point-of-view of spiky, fiercely intelligent 15 year-old Minnie (Rona Morison, sensational). What starts out as larky, dirty fun becomes increasingly more uncomfortable and harrowing as we realise that what we are actually dealing with here is child abuse.

Alexander Parker and Amy Ewbank's colourful, fluid production – the gloriously garish period design is by Andrew Riley – lulls us into a false sense of security with cute projections and blasts of period music. If the first twenty minutes feel like watching a cartoon made flesh, by its conclusion the play has become a disturbing, thought-provoking depiction of innocence forever tainted.

If Heller's adaptation is too episodic to be fully satisfying as drama, it does sound authentically like the musings of a gauche, horny teenager who suddenly finds herself in situations she is not emotionally equipped to deal with. Since we are seeing other characters through her eyes, her abuser – who is also her mother's boyfriend – is treated at first with a remarkable lack of judgement, and Jamie Wilkes' fine, admirably restrained performance reflects that: he is by turns warm, kind, attractive, then weak and, frankly, pathetic. The foul-mouthed dialogue is undeniably harsh but never seems inauthentic.

Morison is astonishing, moving from gauche, tomboy-ish kid through hysterical virago then drug-fucked victim to maturing almost-woman with an assurance and technique that is truly astounding. Her Californian accent is flawless, and her final declaration to her abuser of "I am better than you" simultaneously chills the blood and has you wanting to punch the air. She is worth the price of admission all by herself.

The usually superb Rebecca Trehearn feels miscast as Minnie's free-spirited mother: despite being a likeable stage presence, she reads as too young, too restrained and too sensible for a woman whose ex-partner describes her as a woman who doesn't abide by any of life's conventional rules. The scene which exposes the extraordinary dysfunction of this family where she suggests her boyfriend and daughter get married because they've had sex feels tepid where it should be shocking.

Saskia Strallen does lovely and lively work as Minnie's mismatched best friend, and Mark Carroll impressively embodies all the other men in the story, including Minnie's deeply flawed former step-father.

This is a troubling piece: given the incendiary subject matter, it feels as though it should be more overtly dramatic than it proves to be; and yet because this is life, however screwed-up, refracted through the prism of a smart, sensitive, damaged teenager, the ambiguous tone feels strangely accurate. Cautiously recommended.

The Diary of a Teenage Girl runs at Southwark Playhouse until 25 March.