Creating a little terror

An hour sipping coffee with Aisling O'Sullivan is far more entertaining than an evening in an Irish pub.

She's better looking than most of the characters you find in Irish pubs of my acquaintance. Taller, too. "I am very tall," she says, with a laugh that rattles the cups on the distant counter. "I am very tall and very loud and not a very skilled actress at the moment." She is 5ft 10in and very skilled indeed. "Well, I'm not that tall. I was a lot bigger until I did this play called The Famine at the Abbey Theatre in Dublin. I played a famine victim and went to a dietician and lost a dangerous amount of weight. Mind you, I suppose since then I've gone back to being this giantess."

It is easy to be beguiled by O'Sullivan, star of the revival of The Duchess of Malfi that will celebrate the Royal Shakespeare Company's 40th season in the capital. She's bright and funny and can turn the most mundane anecdote into a riot. Her humble beginnings in the profession, for example. It wasn't an auspicious start. Trying for a place on a course at the Gate Theatre, Dublin, she decided to do a piece from Macbeth and to play Lady Macbeth as if she were pregnant. "I stuffed a pillow up my dress," she recalls, shrieking with laughter, "and they took one look at me and said, 'No thanks'."

So she went back to London, where she was selling insurance for a living. Before this she had made sandwiches in Germany and been a waitress in New York. It was her "big adventure", during which she travelled far from her home in Kerry, while working out what to do with her life. "Nothing seemed to fill me with enormous desire," she says. But through the stories her schoolteacher father told and the plays he asked his class to devise and perform when she was a child, "I became the great director and thought I was going to become a fascist political leader because I loved telling people what to do. "I knew in my gut it was the last year I had of trying to do something in the arts, the last year before I'd have to turn to an office job or something." Hence the pillow up the skirt, which created a strong enough impression for her to be accepted on the drama course when somebody else dropped out.

After that she left scorch marks along the route to major stage roles. She won a contract at the Abbey Theatre and arrived back in London, at the Royal Court, with the company's production of Billy Roche's The Cavalcaders. Then came Playboy of the Western World at the Almeida, where she was spotted by producer Thelma Holt and offered a tour of The Seagull.

It's been a bullet train ride since, with the stops along the way - Tony Kushner's Slavs! at Hampstead, Martin McDonagh's The Cripple of Inishmaan for the National, Strindberg's Miss Julie at the Haymarket - ensuring that she travelled first-class. But she has, she quickly points out, auditioned for almost every role she has played, including the Duchess.

She is impressed by and grateful for the RSC's sophisticated infrastructure, especially the voice coaching that is helping her to overcome the terror of tackling her first verse play. John Webster's 1613 classic is dominated by the Duchess, the widow who opposes her brothers and marries against their will, with tragic consequences. "I've never seen it performed," says O'Sullivan, "but it is an amazing play and an amazing part, and the director, Gale Edwards, is, well, amazing. So I feel comfortable enough in the role

... I'm terrified, of course, but hopefully it is creative terror that will produce absolute focus."

She recently completed filming an episode of a series of three single dramas, to be screened later in the year by Channel 4 under the title Shockers. In Parent's Night she plays a mother whose son commits suicide after being bullied at school and who exacts violent revenge. The part is that of a hysterical woman, a type she has played before on TV. In The Wyvern Mystery, for example, she had to wail and scream and thrash about. "It was hysterically brilliant and I was way over the top. In future, if I am to play roles like that, I am going to stand and not move anything. On TV you have to make everything small, bring it way down, but make it enormous inside as well."

Only the TV series Life Support, in which she starred as a medical ethicist, failed to captivate audiences, although several critics liked it. "It was a terrifying experience. I took the job without realising that constructing a character over six episodes is quite a skill. I take off my hat to people in Coronation Street and shows like that, who are under a microscope all the time."