Hayley Atwell spent months getting in shape for her blockbuster debut in Captain America: The First Avenger, but the actress has revealed her first training session left her feeling rather unwell.
"I turned green and threw up the first time, but then got used to it," she laughed at the film's world premiere in Hollywood.
But the British actress insisted she did learn to love the gruelling exercise regime she was put through "eventually."
She said: "I did about two and a half months before we started filming, and then for the duration of the five month shoot - it was pretty rigorous but absolutely worth every moment."
Atwell, 29, previously known for her roles in Brideshead Revisited and the Duchess, plays freedom fighter Peggy Carter in the superhero movie.
She said she was drawn to her character because: "She has a very strong voice, and can stand up for herself. That's certainly what was appealing to me about playing her."
Looking stunning in a low-cut red dress, Hayley admitted she was thrilled to be walking a Hollywood red carpet.
"It feels a huge honour," she said. "Since I was a little girl, I've always wanted to come down this street and be a part of something in some way - it's a dream come true."