The Oscar-winning actor can be seen in the lead role as transgender artist Lili Elbe in a photo tweeted by production company Working Title.
Reports suggest that Redmayne is losing weight to play the fascinating character, who was one of the first to undergo gender reassignment surgery in 1930.
Due out sometime in 2016, director Tom Hooper originally cast Nicole Kidman as Elbe but she dropped out after shooting was delayed several times.
Based on David Ebershoff’s fictionalised account of Elbe’s life, the story follows Danish painter Einar Wegener’s journey from posing in women’s clothes for his wife Gerda, played by Alicia Vikander, after a model failed to show up, to becoming a woman.
Lucinda Coxon has written the script, which Hooper first read while he was making 2010 Oscars hit, The King’s Speech.
“I was so moved by this true story. I have wanted to make the film ever since,” he told The Hollywood Reporter. “The Danish Girl is an extraordinary love story and a story about finding your true self.”
Amber Heard, Ben Whishaw and Matthias Schoenaerts also star in the film, which is already being tipped for next year’s awards season.Reuse content