Bel Powley, 23, comes across as the sort of person you want to share your secrets with. She’s unflinchingly direct – it’s infectious and one of the reasons she’s such an impressive actor – all honesty, no vanity.

On set, Bel chats about fluids and functions (the bodily sort) with a non-judgemental frankness that makes you feel secretive. She also makes an unpopular confession: an indifference to animals. ‘I wouldn’t want to have a cat or dog because I get really unnerved by the fact that they’re always naked.’ Sure. And even when she says: ‘I personally think sugar is quite evil’, it sounds sincere, not smug. Bel lays it on the line with conviction, and right now she’s carving out a career entirely on her own terms. 

Earlier this year Bel was the toast of the Sundance film festival for her emotionally and physically exposing performance in The Diary Of A Teenage Girl. The film (set in San Francisco in 1976 and based on a graphic novel by Phoebe Gloeckner) tells the story of Minnie Goetz, a 15-year old who has an affair with her mother’s much older boyfriend (played by Kristen Wiig and Alexander Skarsgård, respectively).

In the wrong hands, this charged sexual scenario could have fallen victim to lumpy Lolita-style clichés or heavy handed moralising about manipulation but Bel (who’s in every scene) and director, Marielle Heller, had other ideas: ‘We didn’t want it to be a film about a 15-year-old having sex with a 38-year-old man,’ says Bel. ‘We wanted it to be a film about a girl discovering her sexuality, growing up and becoming a woman.’

Cinema is certainly not saturated with intelligent, make-you-feel-less-alone coming-of-age films that spotlight the female experience. After Ghost World, Heathers, Mean Girls, An Education and The Virgin Suicides, we’re starting to draw blanks. The Diary Of A Teenage Girl is a welcome addition to this select club. The film nails the twisted complexities of the physically and emotionally rattling experience of becoming a woman: seeking love and acceptance, finding purpose and wading through whatever mess your family may have made for you. It’s achy, insightful and unromantic, and Bel is utterly convincing as the protagonist.

‘The point of the film is so important to me: to make female sexuality less taboo, and also to show a normal 15-year-old’s body on screen, which isn’t some Hollywood hairless, blonde, tanned, big-boobed girl. I wanted to do those two things so much that it kind of overrode me feeling uncomfortable.’

And you would have forgiven Bel for feeling uncomfortable. There are seven sex scenes in the film (read: essential nakedness) and her first week on set involved shooting all those scenes back to back. In a nutshell? ‘Tiring and emotionally draining’. Her litmus test was that when she first read the script she didn’t think, ‘Oh god, that’s a film with loads of shagging in it.’ What did strike her was the way the writing captured what it’s like to be a teenage girl so honestly that it's relatable.

‘One of my favourite lines in the film is: "All I can think about is the fucking. Does everyone think about fucking as much as I do?" Every 15-year-old girl has probably thought, "Oh my god, am I weird because I’m feeling horny?" Because no one will talk about it with each other.’

The film sits easily alongside the work of confessional, conversation starter Lena Dunham and, unsurprisingly, Bel is a fan: ‘I’m reading her book, Not That Kind Of Girl, at the moment, she’s just a tour de force. And she said something in it that really resonated with me in terms of the interviews I’ve had for Diary. She said, when people say to her ‘You’re so brave to show your body like that in Girls,’ she thinks, ‘The subtext of that is: you’re so brave to show your imperfect body in Girls’. And I’ve had that so much in Diary, people telling me, ‘that’s such a brave performance’ – they’re saying it’s brave because I’m not perfect. It’s just so interesting.’ 

Bel grew up in West London and both her parents are in the industry (her mother, Janis Jaffa, is a casting director, her father, Mark Powley, an actor). They’re successful, but not famous. The mention prompts an eye roll: ‘I just grew up with it, it was incredibly normalised for me. We weren’t, like, a glamorous, showbiz family.’

At 5ft 2 with a delightfully animated face, Bel looks younger than her 23 years. ‘Sometimes people can be patronising, and I just want to tell them, "I’ve been doing this for 10 years!"’ Since the age of 13, she’s worked steadily in a clutch of British TV series (with a view to paying her way through university) but it was her West End outing in English playwright Polly Stenham’s Tusk, Tusk in 2009 that shifted things for Bel. ‘This whole world opened up to me. It sounds ignorant, but I didn’t know about the gravitas of the London theatre.’ Her performance was attention-grabbing and a Broadway show, Arcadia, followed in 2011:  ‘I was going to study history and politics at UCL, and then just never went.’

Her upcoming projects include a bound-for-success sci-fi/ romance Equals, starring Kristen Stewart and Nick Hoult, and she’s also signed to a film directed by feminist Haifaa al-Mansour (the first female Saudi filmmaker) about the love affairs of Frankenstein author Mary Shelley (played by Elle Fanning) and her stepsister Claire Clairmont (Bel).

Well-rounded female characters, defined by much more than their relationships with men, are what Bel is seeking. She’s determined to avoid the ‘2D’ female characters Hollywood seems fond of, specifically: ‘The virginal princess waiting for her prince charming, the don’t-give-a-f*ck slut, or the really sarcastic asexual.’ She’s just wrapped up on Detour, where she plays a stripper with an abusive boyfriend, highlighting her belief that every female experience is valid. What’s crucial is the way the story is edited and from whose perspective: ‘That was still a very well-rounded female character. I think people get confused, people think ‘strong female characters’ mean you need to play an action figure.’

Bel is quick to acknowledge the advantages of having Diary as her breakout role: ‘I’ve set the bar high in terms of having a very feminist attitude towards how I present my body. I’ve laid it out there physically and emotionally in this movie and people have responded to it so well, it’s made me feel much more comfortable in my own skin. There are pressures, of course, and no one can deny that, even if you’re not an actress there are pressures – we all know that society projects images and ideas of what a woman should be – but I try really hard to not let them affect me.’

From where Bel is standing it’s an exciting time to be a woman in the film industry. Sure, there’s still a pay gap, gender double standards exist (especially regarding beauty) and seeing a woman in the director’s chair remains big news, but the industry is finally discussing the disparity. To be in the thick of that is exhilarating, it’s certainly ignited Bel’s ambition and she’s relishing her part in the wider conversation about women in film: ‘I’m going to nail this, for girls… I feel confident that I’m presenting myself in a feminist way that is good for young women.’

Bel Powley is nominated for the EE Rising Star Bafta Award 

Words: Georgia Simmonds

Pictures: James O Roberts