Altuzarra top, $3,600, similar styles at Barneys New York, New York, 212.826.8900; Ippolita earrings, $795,

Photography by Kenneth Willardt
Styled by Samantha Traina

At the Sundance Film Festival in January, the British actress Bel Powley, 23, caused a huge sensation with The Diary of a Teenage Girl, in which she plays an American 15-year-old who has an affair with her mother’s boyfriend. “It was insane,” Powley said, calling from the set of Detour, in South Africa. “When I saw the sex scene on a massive screen, I thought, Whoa, girl—that was brave!” she said, laughing. “But I’ve been acting since I was very young, so I don’t shock easily.” When Powley was 13, she was cast as a child spy on the British series M.I. High and has been working nonstop ever since. At 18, she left her family in London (her father is an actor; her mother is a casting agent) and moved solo to New York to star in Tom Stoppard’s Arcadia, on Broadway. “That was the turning point,” Powley recalled. “Until then, I considered acting a temporary diversion. Now, I can’t imagine doing anything else.”