Ice baths in the early hours would not be everyone’s choice, but they were just the thing to prepare Posy Sterling for her lead role in the upcoming UK indie drama Lollipop. “I would get picked up at five in the morning so I’d be up at four in an ice bucket outside,” she recalls. “It is extreme, but it’s so good for your mental health and would get me ready for the day.”

Produced by Parkville Pictures and backed by BBC Film and the BFI, Lollipop — the debut fiction feature from documentarian Daisy-May Hudson — tells of a woman who, fresh out of prison, finds barriers in her path towards regaining custody of her two young children. The character struck a chord with Sterling, many of whose credits — including the just-completed run of Dixon And Daughters at London’s National Theatre — have come through her affiliation with Clean Break, the theatre company whose work addresses the experiences of women in the criminal justice system and whose development programme for young artists brought her into the acting profession.

“I read the script seven times before I went in to audition and I fell in love with it,” says Sterling, who grew up in London and Market Harborough in Leicestershire and trained at Italia Conti. “Molly is put through a lot of challenges and may make decisions that others would not agree with, but at the same time you see a lot of joy and hope.” Music was a way to get into her psyche — “she loves R&B classics” — and also helped during a chemistry read with co-star Idil Ahmed. “I don’t know why, but I know the words to ‘21 Seconds’ by So Solid Crew,” she laughs. “So I spilled all the bars while Idil was being the best hype girl ever.”

Sterling had fine role models on which to draw, having filmed with Saoirse Ronan on addiction drama The Outrun for director Nora Fing­scheidt, and with Jonah Hauer-King on BBC Second World War series World On Fire before Lollipop began shooting. “They’ve both done loads so I learned so much from them,” she says. If there is one person Sterling would like to take tips from, though, it is Olivia Colman. “I love the scope of what she’s done over the years,” Sterling says. “Whatever genre it is, she absolutely smashes it.”

Contact: Olivia Woodward and Alex Sedgley, Curtis Brown