FILM: Diary of a Teenage Girl - A warning to parents

An art-house masterpiece that will be talked about in 20 years - but parents of girls should think carefully before watching.

This film will be spoken about in 20 years. It's an art house masterpiece and then some, like Taxi Driver. Bel Powley will become a household name from her performance as a 15-year-old who has sex with her mother's 35-year-old boyfriend, played by Alexander Skarsgard.

It plunges you into 1976, bathed in the dusty, orange light of a decade that threw off the mistakes of its forefathers and took bolt cutters to the white-shirted respectability of the 50s and 60s. In every shot you feel the era.

So what's not to love? As I watched it with two friends who'd raised sons, I paused. What would the parents of girls feel watching this? The director Marielle Heller was reportedly unimpressed at the film receiving an 18 certificate in the UK - but I think another warning should be added.

The mix of body and beauty insecurity and the overwhelming flood of hormones in the teenage years are scary for parents to contemplate. I'd think carefully about how you talk about it to the parents of girls if you're lucky enough to see this film - which at some stage you will.