Working with a theatre company for women affected by criminal justice has given the actor a passion for stories that fall between society’s cracks. Now she is swapping Broadway for a powerful account of Britain’s broken prison system

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ach morning before filming Lollipop, Posy Sterling took a giant bucket outside, filled it with ice and climbed in. Never mind that it was November or that her call time was at 5am; the actor would take daily dips in the freezing water in the dark. In Lollipop, Sterling plays a headstrong mother who has recently been released from prison and is fighting to win back her kids. The role is heavy, but the ice baths meant she started the days feeling light. “I just found it euphoric,” she says. Tickled, her driver started bringing her more ice as part of her ritual.

Today, Sterling, 32, is similarly full of beans, buzzing from two coffees and fresh from six weeks in New York. “I haven’t slept,” she says brightly. The actor has been quietly building her profile since Screen International named her one of 2023’s Stars of Tomorrow, with performances in the Saoirse Ronan addiction drama The Outrun and Benedict Andrews’s buzzy take on The Cherry Orchard at the Donmar Warehouse in London, which has just finished a run off Broadway. We’re meeting in an office in north London, where Sterling is excited to talk about her first leading role in a film.