You may not recognise Andrea Riseborough from one role to the next, such is her acting talent, but get used to hearing the name

ANDREA RISEBOROUGH is on the brink. The 29-year-old English actor has worked consistently since graduating from the Royal Academy of Dramatic Arts in 2005. She played Miss Julie in a highly acclaimed production of Strindberg's play at the Theatre Royal in Bath. She had a supporting role in Mike Leigh's Happy-Go-Lucky. Indeed, it is a source of pride that in the years since leaving drama school she hasn't taken off a single day.

Riseborough's career is about to ram into hyperdrive. The trigger was her turn as a young Margaret Thatcher in the delightfully unreliable 2009 TV movie The Long Walk to Finchley. Since then directors have been clamouring to get Riseborough in their films. She was the beehived, promiscuous striker in Nigel Cole's Made in Dagenham.This week she turns out as Rose, repressed girlfriend of the vile gangster Pinkie, in a curious reinvention of Graham Greene's Brighton Rock.Next week she is convincingly Irish in Mark Romanek's Never Let Me Go. Most intriguing of all, later in the year, we will see her as Wallis Simpson, wife of the sometime King Edward VIII, in a film by Madonna.

“It’s very hard work, I can tell you,” she says in her strong, actorly voice. “When I was at Rada I’d get there an hour early every day. It doesn’t come easy.”

Riseborough is prone to the odd bout of luvvie-speak. In a recent interview with the Guardianshe let loose the following extraordinary phrase: "Shakespeare opened the door for me dramatically. It was William. My friend William."

She cuts a striking figure. Everything is long: long hair, long face, long body, long vowels. But, like many of the best performers – and she is very good indeed – she is so adept at losing herself in the work that she can be hard to recognise from one role to the next.

Emerging from Never Let Me Go,a colleague refused to believe me when I explained "the Irish girl" was the same person who essayed the Iron Lady (or Margaret Hilda Roberts as she was then known) in The Long Walk to Finchley.

“Oh really,” she says. “Well, that’s lovely. That change is the thing you work for internally. You may not see much visible external change. But people operate on so many levels. It may look like you’re doing nothing. But there’s months and months of work you don’t see. I don’t mean that to sound sententious. But we do work hard.”

There’s a lot more where that came from. By golly, Riseborough can chat. Ask her about Brighton Rock and, while you nervously watch the clock tick towards the end of your allotted interview time, you will be treated to an eloquent dissertation on the nature of Graham Greene’s Catholicism.

The voice is interesting. The precisely struck consonants and Shaftesbury Avenue vowels betray her Rada training, but there is still a strong hint of the northeast in there from her upbringing in Whitley Bay, a seaside town a short distance from Newcastle-upon-Tyne. Dad was a self-made man. Mum was a former secretary.

Was she a show-off as a kid? “A show-off? Oh, no, no, no,” she says, adopting a degree of (I think) mock outrage. “You know, I don’t think actors are, very often. I think it’s the opposite way round. When I was little I was quite solitary in lots of ways. I always liked film and Shakespeare. Those two things were like lifeblood for me.”

Recalling her passion for afternoon matinees of classic films on TV, she mimes pressing her face to the screen and cupping hands round her eyes. “I felt sure I could see what was happening outside the box. If I look hard enough I can maybe see what’s happening over there in the corner. I loved all sorts of things, from Peter Sellers to Ingmar Bergman. My dad is a great fan of old movies, so we talked a lot about that.”

The young Andrea was edged towards Oxford by her teachers, but, as A-levels loomed, she had already decided to try her hand at acting. As she perceptively explains, it’s hard to see in what way an English degree offers you much to fall back on if the roles refuse to come. At any rate, no such problems developed. Racking her brain, she can recall only one significant period when she wasn’t on stage or before the cameras.

“I did decide, at one point, I needed some time away from academia. Cut to me shredding duck in a Chinese restaurant which I was kind of running. As I was shredding duck I was thinking of Chekhov. What a geek. Duck leads to Chekhov. I was thinking, while doing that, This is probably the last time I will do anything like this.”

And so it transpired.

Four years after graduation, already something of a rising star on stage, she broke above ground with The Long Walk to Finchley.The TV movie is a wonderfully slippery piece of work. Tony Saint's script imagines that, while desperately searching for a seat, the young Margaret Roberts attracted the eye of Edward Heath and that his subsequent antipathy towards the mature Margaret Thatcher was born out of this early infatuation.

When I ask how researching the part altered her attitudes to Thatcher, Riseborough focuses on the physics of the performance rather than the chemistry. She refers to inclinations, to gestures, to grimaces. “It was an aspect of her life that hadn’t been explored,” she says. “There’s no material on that period. So you have to work backwards to find out what she might have been like physically in terms of character. It’s to do with the way she moves her body. It’s not about the tension in the muscle. It’s about the reason behind the tension in the muscle.” As she says this she leans forward and punctuates her point with a forceful and distinctive nod of the head.

That was a Thatcher nod. Wasn’t it? “Yes. That’s my point. I’m glad we’re on the same page.”

You can see certain connections between Thatcher and Wallis Simpson. Both have, in the years since their pomp, become figures of hatred for the British public. The portrait of Mrs Simpson – and her eventual husband – in The King's Speechis quite merciless. Eve Best practically cackles in the role. Gillian Anderson was even more beastly in the recent TV adaptation of William Boyd's Any Human Heart.

From what Riseborough says, W.E., as Madonna's film is currently titled, is attempting a revisionist take on the American divorcee. The actor is keen to explain how Stanley Baldwin, then the British prime minister, worked hard at poisoning minds against Simpson. It doesn't sound as if she'll be making a vampire of the eventual duchess of Windsor.

“She is only hated in [England],” she says. “Everywhere else she is kind of a sweetheart. It was extraordinary to me, doing the research, how effective Baldwin’s propaganda was. We were never given the opportunity to have a fair opinion of her.”

What about meeting Madonna? “I wasn’t nervous at all,” she says. “You may think you know somebody like that. But of course you never really know them until you actually meet them. And she is absolutely wonderful. She is so strong. She is such an endless inspiration.”

We won't see W.E. until at least the end of the year. But, before then, we have plenty of Riseborough to be going on with. Despite appearing alongside such mighty talents as Helen Mirren and John Hurt, she is the best thing in Brighton Rock.

Sassy in Made in Dagenhamand imperious in The Long Walk to Finchley, she somehow becomes a believably sat-upon waitress in Rowan Joffe's film (which updates Greene's 1938 novel to the early 1960s). Did she understand how a "nice girl" could fall in love with such an irredeemably bad egg?

“That’s for you to answer. I think I do because I have felt love and I understand what that means. It’s our job to make you understand that sort of emotion. I think she feels that Pinkie is like an angel come down from heaven in her drab world. I can’t say if I got that across.”

It seems as if she thinks deeply about her work. "I don't know about that. I think I feeldeeply about it. That's a different thing. I feel deeply about it."

Message understood.

Brighton Rock is on general release