It's hard to think of an actor better suited to the lead in Lone Scherfig's adorable Their Finest than Gemma Arterton. The Kentish actor stars as a screenwriter working on a patriotic film in London during the second World War. Dark, nicely spoken with classic English features, Arterton could have been plucked unaltered from a picture by Michael Powell or the Boulting Brothers. The film within a film – a Dunkirk adventure concerning plucky twin sisters – looks like just such a project.

“We were so excited about that,” she says. “The technicians loved getting all the old equipment out and shooting in the old style. We even shot all of the Dunkirk stuff in the oldest studio in Pinewood. It even smelt right.”

Yes, I half expected John Mills to pop up in the studio's water tank. This is where they shot The Cruel Sea, I imagine. "Yeah, yeah," she laughs. "He was in practically every film at that time. Maybe he was hiding behind one of those huge lights."

A lot has changed since those times. A lot has not. Their Finest has much to do with the role of women behind the camera. Figures suggest that the industry, over the past 70 years, has progressed painfully slowly towards gender equality. Their Finest may be directed by a woman, but we still have a long way to go.

“To be honest, I don’t think it has changed much until quite recently,” Arterton says. “It’s been in the media a lot and it’s now on the agenda. People are making an effort. The problem for me has been the lack of female screenwriters. There are great initiatives out there. But it has been very slow until recently.”

Working-class background

We can, at least, argue that attitudes to class have transformed since the second World War. Or can we? To most Irish ears, Gemma Arterton, a distinguished graduate of the Royal Academy of Dramatic Arts, stops few glottals and drops few h’s. But the subject of her working-class background has arisen in interviews over the years.

Last year, writing for The Guardian, film critic Danny Leigh described her early career as a good example "of the assault course a young British actor has to contend with. But specifically, a working-class actor."

In the new century, the public schools have fought back against the egalitarian gains of the 1960s. Has she ever failed to get roles because she wasn’t posh enough? Would she know if that had happened?

“Errr . . . I don’t know,” she says. “Roles my contemporaries got? I can only speak from my personal experience. There have definitely been times when I have not got jobs because it was thought I was not posh enough. I know that. But I am about to play Vita Sackville-West, who is the poshest person there ever was. I think maybe it is a bit of a myth. Don’t forget that actors choose. Not all actors want to play posh. Ha ha!”

Arterton was born in Gravesend, the daughter of a cleaner and a welder. She began acting at school and fought her way into Rada on a scholarship. I get no sense that she was ever out of work for long.

“I never thought I’d work in film,” she remembers. “I always thought I’d be just a jobbing actor in the theatre. I remember in my third year at Rada, I did a budget – about the only one I’ve done – calculating how much it would cost to live in London. You are told you might work once a year. That’s the life.”

Film career

While still at drama school, she got a role in a Stephen Poliakoff film for the BBC. In 2008, then still 20, Arterton was cast as Strawberry Fields in the Bond film Quantum of Solace and as the lead in a TV adaptation of Tess of the d'Urbervilles. The "Bond Girl" tag can be a bit of an albatross.

Many are the actors who fail to capitalise on that supposed big break. But Arterton dug in. We shall say as little as necessary about the St Trinian's revival. She had better luck with Stephen Frears's Gemma Bovery and the excellent horror The Girl With All the Gifts.

Meanwhile, Arterton was consolidating a formidable reputation on stage. In the past year alone, she has played Saint Joan and Nell Gwynn. She also excelled in the musical version of Made in Dagenham.

“The theatre has always been my first love,” she says. “I just love it. I love to be able to go out and just do a play. I like to be able to tell a whole story and have it be a little different every night. I love that challenge. I love to take on something really difficult and work at it. That’s why I became an actor.”

She’s been through the wringer in her personal life. A marriage to Stefano Catelli ended in 2010 after five years. Other relationships have sparked and then fizzled. But, still just 31, she has shown a commendable determination to control her own destiny. Rebel Park, an all-woman production company she helped establish, is pushing ahead with comedy, TV series and film. She is set to play Vita Sackville-West, writer, garden designer and romantic partner of Virginia Woolf, in a film produced by the Irish company Blinder Films.

“Yes. She is a huge character. I don’t want to do her a disservice and she’s never been properly depicted,” she says. “Eileen Atkins wrote the screenplay and she’s not posh either, let me tell you. From East London, not that you’d know it. She saw me in a play and thought I could do it. I was very touched because she has played Woolf many times and it’s part of her life.”

The British film industry needs a few more like Gemma Arterton. She has movie-star presence and the wit to shape the medium to her needs. Not that she sees it that way. She still sees herself as being buffeted by the winds.

“Oh, I don’t know. I’m a coaster,” she laughs. “If it hadn’t worked I’d have found something else to do. It’s so precarious. Things fall apart. It’s mad. It’s not a job for anybody who wants to plan.”

• Their Finest is released on April 24th.