ON THE train journey to meet Andrea Riseborough – passing through her home city of Newcastle, then Grantham, birthplace of Mrs Thatcher, who she memorably transformed into a sexpot – I decide she's going to be intimidating. This is an actress, after all, who's been a devotee of Shakespeare since the age of nine.
But seconds after arriving fashionably late, dark glasses at noon, in a borrowed fur coat (on loan from a yeti, I'd guess), she's ordering a gargantuan breakfast, speculating on the rules of our London rendezvous' Honesty Bar, launching into the first of a series of silly walks to illustrate a point – and confiding in me her deep love for Aviemore's Cyril the Squirrel Club.
"My mam and dad honeymooned in Aviemore, so every year they dragged me and my sister Laura back there," she says in Geordie tones as robust as stottie cake. "One of the hotels, the Four Seasons I think, laid on fun for kids – Cyril the Squirrel, Bunny Blue and a badger whose name I've sadly forgotten – and back at home we'd make up plays about these characters in our bad Scottish accents."
So would she say it was this experience, rather than the Bard, which inspired her to become an actress? "Ha ha, well it was probably a combination of the two. Yes, Cyril and Will, fine storytellers both, and that's what acting's about really." There's a theatrical pause, and then comes the punchline: "Oh, and by the way, Aidan, I was eight when I first got into Shakespeare."
Over the course of the next hour and a half, Riseborough will address me by my name no fewer than seven times – a record for an actress who isn't American or in therapy, or both. But she also scribbles down her mobile number and tells me to call if I ever want to see her seduce Kenneth Branagh on the West End stage. No actress, from anywhere, has given me their number before. I sense in the funny voices and witty asides which embellish her anecdotes that I'm being treated to a bit of a performance today. But all the same, it's a very good performance. Riseborough, who's 28, single and currently playing Chekhov, is much raved about, and in my little private theatre in Covent Garden I can understand why. She judo-throws the yeti to the floor to reveal a skinnymalink frame and I wonder where she's going to put all that food. The patterned dress, tucked into men's trousers, is by Ozzie Clark and another borrow. Her features – auburn hair, worn up, grey-blue eyes, pale skin, full lips – are her own, but I'm beginning to think they might be on hire as well.
I always considered myself the office expert on Party Animals, the BBC spin-doctor drama which spun many of its cast into telly omnipresence. But before this interview, a colleague remarked: "Your girl Andrea was in it." I didn't register this, and yet I'd fancied her character, Kirsty. The ability to disappear completely into a role is surely the mark of a great actress.
Kirsty used her sexual wiles in a politically charged world and so did Riseborough's Maggie in The Long Walk To Finchley, also for the Beeb, when she blubbed and flashed a shapely calf to charm old Tory buffers and then propositioned Ted Heath. In The Devil's Whore, Channel 4's blockbuster about the English Civil War, she's at it again, albeit more innocently, as Angelica Fanshawe, a young noblewoman who has her head turned by the anti-monarchist cause and by John Simm's mercenary ("How got you those cuts?" she asks him early on). This pistol-for-hire keeps himself alive when wounded in battle by summoning up images of her violet garters, as one would.
By episode two, after the execution of her husband, it's being said of Angelica: "Upon my life, this woman is the epitome of wickedness – she consorts with men!" Angelica isn't a whore, adds Riseborough, just "innocently, naturally sexual" at a time when that got you burned at the stake. "Back then, female sexuality wasn't understood. I've read up on this and even the female orgasm wasn't understood. For a woman to come was a sign of conception and therefore highly sought after." Riseborough has nude scenes in The Devil's Whore, as she had in the Sam Taylor-Wood short film Love You More. She doesn't have a problem with them, or with body image. "I'm very happy with my wonky bits. Mind you, this script had the worst stage direction ever. It went: 'She pulls back her veil and they're all astounded by her beauty.' When I read that I just thought: crapsticks. Crapsticks and knob ends."
Filmed in South Africa, with the veldt doubling for Oxfordshire, The Devil's Whore has been co-written by Peter (Our Friends In The North) Flannery and stars Dominic West from The Wire as Oliver Cromwell and Peter Capaldi as Charles I. Riseborough talks knowledgeably of the civil war and its legacy, or lack of one. "We had a revolution a short time ago but even though it was for a just cause we're not proud of it, like the French are of theirs. In France now, they strike three times a bloody week. Our attitude is: 'Mustn't grumble.'" She's obviously done her research – about orgasms, the lot.
"Joan Didion (the writer] says, 'Go back to the literature' and that's what I always do to prepare for a part. I read four great historical novels for the four different periods of Angelica's life. I listened to four different composers, wore four different perfumes – even four different kinds of knickers." She's noted for her swotting. For Thatcher, she visited the Iron Lady's old bedroom in Grantham, which is now a massage suite in a holistic retreat. For the role of a chav in the play that persuaded Mike Leigh to cast her in Happy-Go-Lucky, she risked confrontation with the real, tooled-up thing on a late-night bus touring a rough estate.
At first glance of her biog, it's not obvious how Riseborough became an actress: her father was a car salesman, her mother a secretary and beautician. But then she reveals her mum has a Masters in Shakespearean and Jacobean studies and her dad is a movie buff who introduced her to Brando, a pivotal moment. "I couldn't hear what he was saying and I realised: acting can be this good and you can be that brave."
Her young life was one of vivid contrasts: of throbbing city and faded, genteel Whitley Bay, of state school and private college (class difference was a Tracker bar), of a family from solid mining stock bettering themselves under Thatcher. There was much for young Andrea to observe, and the observation which is starting to follow her around is of the "aspirational cocktail sausage" which suddenly appeared on the dinner-table, along with Black Forest Gateau. She says she doesn't want to be seen to be mocking her parents, who gave their daughters everything, but can't resist adding today: "We experimented with vol-au-vents as well."
What better world in which to develop these observations than acting? But Riseborough – who wanted to act so much that she flunked school – then lost the urge. She blames a mixture of "hedonism, adolescent frustration and love" so she did odd jobs, made greetings cards, sang with a band and ran a Chinese restaurant with her rollerblading best friend, Cyan Wong. "I went a bit wild, I was a worry to my parents, but I also grew up. Cyan and I shared a single bed in Jesmond and one night we scribbled on the ceiling: 'See you in our London pad.' Now we live together in Hackney and she runs a style bar in the building on the cover of David Bowie's Ziggy Stardust album – what a great job."
It is, but so's Riseborough's. She's so in demand that her idea of a hobby is "nipping into the British Museum, standing in the Greek Room among the urns and just breathing". And now Kenneth Branagh awaits. One seduction is over, and another is about to begin.
• The Devil's Whore, Channel 4, Wednesday, 9pm