Playing one of the world’s most famous supermodels would be a tall order for any actor—but doing it in the nude? That was the challenge Ellie Bamber took on when she was cast as Kate Moss in the new film Moss & Freud. Directed by James Lucas (in his feature debut) and executive produced by Moss, the film focuses on the making of artist Lucian Freud’s 2002 portrait of the model—and the forging of an unexpected friendship.

Born in 1997, Bamber grew up in Surrey, where she dreamed of the bustle of nearby London. At age 13, she made her professional stage debut in Trevor Nunn’s 2010 production of Aspects of Love at the Menier Chocolate Factory, before taking her talents to Hollywood for Tom Ford’s 2016 psychological thriller Nocturnal Animals.

All along, fashion was a quiet passion; growing up, Bamber covered her bedroom walls with mood boards and lingered over the clothes at her local shopping mall. But for Lucas, the decision to cast her came down to something far more straightforward—and, in a way, incidental: her striking resemblance to his film’s main subject. “Ellie was the only person on my list,” he says. “Someone had sent me a photo of her in some kind of fashion shoot, and I thought it was Kate.” The young actor’s cool confidence only sealed the deal.

To prepare for the part, Bamber underwent a Kate Moss bootcamp of sorts. She dug up every video she could find and studied Moss’s voice and mannerisms. On a runway set up in a church gymnasium, she practiced Moss’s walk, paying close attention to her stride and attitude. She also worked with movement coach Polly Bennett and vocal coach Louise Jones, the latter of whom drilled her on Moss’s signature Croydon accent, making sure Bamber factored in the requisite rasp—and slight air of mischief.

“The big thing that we spent hours on was the laugh, like the cackle,” Bamber says. In fact, it grew into a bit of an obsession—so much so that her younger brother, with whom she lives in London, had to intervene. “Towards the end of filming, my everyday laugh got a bit funny, and my brother was like, you have to stop,” she says.

Bamber also spent some time with Moss—the two had met before, at parties, including one just after she got the part—and wore a few prized pieces from the model’s own archive for the film, pulled by Moss’s friend James Brown. These included a John Galliano Union Jack blazer and a vintage blue sequin dress that Moss wore to her 30th birthday party.

To prepare physically, Bamber stuck to a rigorous workout routine, wore color-changing contact lenses, and dyed her hair. She also had to get comfortable performing nude.

“It was something that I thought about a lot,” says Bamber, “because obviously, Kate has experienced being nude for photographs so much in her life.” At home, Bamber would hold the position that Moss assumes for the painting—though there was also the subtler matter of teasing apart Moss’s comfort as a fashion muse from her vulnerability in Freud’s studio, as she surrendered to his uncompromisng eye.

All the while, Bamber and Derek Jacobi, who plays Freud, worked to cultivate a closeness that comes through on screen. “We met several times before we started shooting, essentially to get to know each other, but what transpired was an unexpected and delightful friendship,” Jacobi writes in an email.

In another instance of life imitating art, Bamber admits that after smoking so much in the film, she picked up the habit in real life—and learned a little something from Moss in the process.

On the first day of shooting, Moss was on set with her. “I had this dressing room in this house, and I was quite concerned about going out and having a cigarette. And I remember her being like, What are you doing? Just have a cigarette in here,” Bamber says.

“It was just this perfect moment—just the naughtiness of it. I needed to take a leaf out of her book and break a few more rules, I think.”

Moss & Freud is now available on VOD.