From elegant English rose to Spanish siren

"I've never felt that I looked very British," she says. "Even so, Consuelo is a departure for me. I'd never wear what she wears – a lot of bling and a lot of make-up, probably the most make-up I've ever worn on a job. But playing a femme fatale is much more fun than playing a goody two-shoes."

For a star of her stature – she has a blockbuster, 2011's Captain America, under her belt – Atwell is distinctly unstarry. She talks frankly about her one-time resistance to red carpets. "I used to say that I didn't do them because I was a serious actress but I remember going to an event five years ago in flat ballet shoes, a skirt I got from a market and a black H&M top. I looked at the pictures after and saw how well turned out all the other girls on my table looked, and they didn't look superficial or vain, they just looked really good. I was so superior and righteous about the whole thing but I looked awful."

Since that experience, Atwell has reappraised her approach to glamming up for premieres. "You have to decide what level you're going to dress up to and what character you're being – because that's a character in itself. I always wanted to be an accomplished stage actress. I wanted to feel it was my currency. Have a craft, a feeling that I could be Helen Mirren when I'm in my sixties and still have sex appeal but it not be what I'm known for."

Shooting in Spain, she was spotted twice. "Well, I've had two people shout 'Colin Farrell!' at me. It took a moment to realise that that's because I was in a film [Woody Allen's Cassandra's Dream] with him." Does the attention bother her? "People staring is a bit disconcerting. I'd much rather people came up to me than stare. Being stared at can make you feel a bit… lonely."

It annoys her when brilliant actors don't get the recognition they deserve. "I was really angry, really riled that Olivia Colman wasn't nominated for a Bafta for Tyrannosaur," she fizzes. "But it's not a fair world. There are brilliant actors whok will never really be known or shun the limelight and limit the choices they have. And then there are those who take huge blockbuster roles and that gives them huge power to go make smarter choices like Keira's done. It's a balancing act, a navigation. No one really knows anything so you make it up as you go along."

Part of Atwell making-it-up-as-she's-gone-along of course includes landing the leading lady role in Captain America (budget: $140m; box office: $369m). Was it an opportunity she found daunting? "I nailed the audition and I knew I had, so I felt I got the job off the back of what I did in the room and not how I looked. That was really empowering. Sometimes you hear horror stories of producers putting doughnuts in front of you to test you or fretting about how much weight you need to lose but I had two trainers who were there because it was an extraordinarily physically demanding part. I wasn't airbrushed in any of the pictures to look smaller. I loved that."