We perhaps overuse the word “transformative” when talking about impressive acting feats, but when it comes to George MacKay’s startling work in “Femme,” it’s hard to avoid. Best known as the resilient soldier in the Oscar-winning WWI epic “1917,” the 31-year-old Londoner doesn’t just change his appearance — with bulging muscles and in-your-face tattoos — but his whole onscreen energy in Sam H. Freeman and Ng Choon Ping’s boldly queer psychological thriller.

As swaggering drug dealer Preston, whose violent homophobia masks desires awakened by Jules (Nathan Stewart-Jarrett), a drag queen with a secret agenda, MacKay is at once intensely frightening and vulnerable — perfectly in tune with a tense, surprising study of toxic masculinity that never tells you where to stand with its characters.

We sat down with MacKay in the Variety Lounge presented by the Zurich Film Festival to talk more about his work in “Femme” and why he’s drawn to playing outsiders — in his words, “the most alive, the most complex” characters — rather than conventional heroes. He also discussed the process of finding Preston’s physicality, including the unlikely actorly game-changer of a full-neck tattoo, and the importance of using an intimacy coordinator in his fraught sex scenes with Stewart-Jarrett, to add “a level of nuance and practicality to something that is also very physical and sensual.”

Finally, he dug deeper to discuss how making “Femme” amplified his awareness of his privileged position in the industry as a white upper-middle-class actor: “As you meet the world you see how much you’ve been encased unconsciously by your privilege … I’m grateful to be part of stories where you invest in people other than yourself.”

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