The supermodel-turned-actress and writer talks to Hannah Stephenson about teenage troubles and how she is now living the dream on screen.

She may look the picture of confidence on the catwalks of Burberry and Chanel, but supermodel-turned-actress Cara Delevingne wasn't always the seemingly fearless bushy-browed fashion icon she is now.

The 25-year-old, whose net worth is rumoured to be £14 million, admits to channelling a lot of her own own teenage angst into her debut YA novel, Mirror Mirror, which centres on four misfit teens who form their own family through a band, as they attempt to deal with the challenges adolescence throws at them.

Some might wonder what this girl from a privileged background - her father, Charles, is a successful property developer and she grew up in the elite enclave of London's Belgravia - had to worry about, but she has said that for a long time when growing up, she never felt good enough and always felt pretty weird and different as a child, so she can feel the loneliness of her fictional characters, Red, Leo, Rose and Naomi.

"Growing up in London, the angst, the hormones, the starting to figure out who you are and what you want to do, and hating yourself and loving yourself and looking at other people, you realise that at the end of the day, it doesn't matter what anyone else thinks.

"It just comes down to who you are and who you want to be," says Cara. "And if you don't know who that is, it doesn't matter. If it's weird and if you want to chop your hair off or dye your hair green or put on a stupid hat, it doesn't matter. Just do what you want to do."

Red, the main protagonist, has an alcoholic mother (Cara's own mother Pandora, a former debutante and model, struggled with addiction to prescription drugs and heroin). Other issues the characters tackle in varying degrees include self-image dilemmas, dark moods, drug-taking, a questionable suicide attempt and confused sexuality. There are several surprising twists in the plot.

When one of the group, Naomi, disappears and is found at death's door in the Thames, with police claiming a failed suicide attempt, the weaknesses, insecurities and dark secrets of the other band members emerge.

Cara too had her fair share of challenges growing up. At 15, she suffered a bout of severe depression, the culmination of a period of anxiety and self-hatred.

She would self-harm, scratching herself 'til she bled, was prescribed anti-psychotic drugs, would slam herself against a tree to try to knock herself out and ended up seeing a string of therapists, she later told US Vogue.

The depression resurfaced when she was 22, but today, she says it's not a recurring theme in her life.

"We all get down, but mental illness is something that's very important that we all need to talk about. I'm very lucky and grateful to be able to do things that I get to do. I work very hard and I just need to make sure that I spend enough time looking after myself.

"Writing the book has certainly been the best kind of therapy I've ever had, for sure, because it's there to help other people in therapy in some way. If you can talk about experiences and other people read it and enjoy it, that's great," she admits.

"When you bottle things up and don't allow yourself to be emotional, when you don't feel things, whether it came out as depression when I was 15 or as psoriasis when I was 18, I tend to bottle things up and brush things under the carpet.

"It's just about learning to express those things, which is why I write music and have learned how to cry."

Music and acting have always helped her escape the more painful elements of her life, she has said. She's already starred in the 2016 blockbuster Suicide Squad and recent sci-fi adventure Valerian And The City Of A Thousand Planets.

Now sporting a new brunette pixie-style haircut, she shaved her hair to star in the forthcoming Life In A Year, in which she plays a teenage cancer patient.

"I'm living my dream, I'm living my fantasy, from when I was a kid. I'm doing a TV show and playing a fairy (in a series called Carnival Row, opposite Orlando Bloom) - it's the coolest thing ever," Cara enthuses. "I'm only 25 and I've already shaved my head for a role, playing a cancer patient. That is incredible, to be able to play these roles."

Writing the book while in the midst of shooting Life In A Year was also therapeutic, she reflects.

"I found the writing process liberating. It was the light at the end of the tunnel. While in the role, I was in a very dark place. Writing the book gave me a window of light."

The novel is peppered with Snapchat streaks, references to WhatsApp, secret Facebook forums and chat rooms, all the online material familiar to any teenager.

"I grew up later, after the social media thing. For me, I would have alienated myself more with it," reflect Cara, who today has 40.6 million Instagram followers.

She also explores sexuality in the book, as the teenagers struggle to find themselves ("Of course. I don't know if any human is able to say if they are completely sure of their sexuality their whole life. I don't think anyone is able to say that...").

It's been well documented that she has dated both men and women, including American musician St Vincent and singer Jake Bugg. She recently told Glamour magazine: "Once I spoke about my sexual fluidity, people were like, 'So you're gay'. And I'm like, 'No, I'm not gay'."

While films and books seem to be the way her career is heading, what about modelling?

"It's something that I'll probably not always do - I don't know if I'm always going to look the way I look - so I don't know," Cara confesses.

"Modelling has been a big part of my life and it's what I'm known for, but it's not something that I've been writing about - but maybe I will one day."

  • Mirror Mirror by Cara Delevingne with Rowan Coleman is published by Trapeze, priced £12.99. Available now