Young British actress Bel Powley, last seen playing Princess Margaret as a flirty, flighty airhead in A Royal Night Out, appears in a very different role in The Diary of a Teenage Girl, a daring coming-of-age movie set in 1976 San Francisco, adapted from the ‘words and pictures’ graphic novel by author and artist Phoebe Gloeckner.

And she delivers another tour-de-force performance, playing a 15-year-old girl who embarks on a heedless affair with her mother’s 35-year-old boyfriend (Alexander Skarsgaard).

Wide-eyed and eager for experience, Powley’s Minnie Goetz is an aspiring cartoonist and her drawings – vivaciously animated by Sara Gunnarsdottir – frequently spill over into the live action scenes.

Confided to her secret audio diary but kept secret from her feckless hippie mother (Kristen Wiig), Minnie’s reckless exploits are certainly provocative, but writer-director Marielle Heller never passes judgement on her characters, giving us an honestly messy account of her heroine’s sexual and artistic awakening.

Certificate 18. Runtime 102 mins. Director Marielle Heller 

The Diary of a Teenage Girl is available on DVD & Digital Download from Entertainment One.