Somebody must have whispered a number in Ms Duncan's ear at an early age - perhaps not a 10, but certainly a seven or eight. She's a woman who never seems in doubt of her status as a class act. On stage she radiates a passionate confidence, a feline concentration that leaves audiences breathless, whether in Tennessee Williams's Cat on a Hot Tin Roof (for which she got the Evening Standard's Best Actress award) or as the decadent, scheming Marquise de Merteuil in Les Liaisons Dangereuses (which transferred from the West End to New York, picking up en route an Olivier, a Tony and the impressively weighty "Theatre World Award for Outstanding New Talent"). On television she can do wifely parts with docile conviction, playing the supportive-but-hopeless Mrs Peter Mayle in the BBC's doomed production of A Year in Provence, or the eponymous, free-thinking clerical spouse in Joanna Trollope's The Rector's Wife; and just as you think you've got her number - as a modern, blonde Celia Johnson, put-upon but gorgeously resilient - she turns up in a spectacular basque playing the femme fatale Barbara in Alan Bleasdale's GBH, or as Al Pacino's missus in City Hall. She is by no means easy to typecast.
She spent much of last year abroad, on a five-month tour of America with the RSC's production of A Midsummer Night's Dream, in which (scoring a definite 10 on the Richter scale of status) she played both Titania and Hippolyta; her husband, the actor Hilton McRae, came too with their five- year-old son, Cal. She returned to star in Harold Pinter's most recent playlet, Ashes to Ashes, at the Royal Court last September. And next week, hardly drawing breath since the close of Ashes, she turns up in another Pinter production, this time his violent, creepy drama of dysfunctional maleness and mass seduction, The Homecoming, which is in preview at the National Theatre.
Sitting in the bar at the National, she is a monochrome dream, her blonde hair so blonde, her black wool outfit so stygian, her blue eyes so Aegean, her wide mouth so Kim Basinger-ish, her cheekbones so stratospheric, her skin so translucent, her voice at once so cut-glass and so dramatically deep. When she turns her queenly gaze to the window, while pondering an answer during one of her frequent long silences, you find yourself considering her beauty as though it were itself on stage, a thing detached from her, as she muses on the curious way she became what she is.
"I've been described as an English Rose," she concedes unhappily, "which irritates me intensely. It sounds so sickly-sweet and it's so limiting; but I can't be described as English anyway." She was born in Scotland. Her parents were working-class Scots, from Glasgow and Edinburgh, who moved south when Lindsay was "five or six", first to Leeds then Birmingham, where she grew up. "When people hear the way I speak, they think I'm from some comfortable middle-class background. But we didn't have a lot of money. We didn't have a telephone or a car. Both my parents spoke with Scottish accents. A lot of expressions they used were Scots army slang... "- she adopted a sudden Iain Cuthbertson delivery - "They uised to say, `Kit'na budgie?', meaning `What time is it?'. I don't know how I spoke but it wasn't Scots or Birmingham. I can remember two friends of my older brother saying, `Ooh, 'ere cooms the Queen' because I spoke posh, but I don't know where it came from." How did her parents feel about producing a middle-class daughter? "Well, it's not an unfamiliar journey, is it? It happens a lot. You just get your hands on the best available education for your children. I got a lot of support from them, even though I went to an ordinary primary school." But was she aware of being culturally distant from her father? "It was so strange - like being brought up on parallel lines. My parents didn't belong in Birmingham. I didn't belong in Birmingham. I just longed for something else."
Her escape was in daydreams, with two distinct plot lines. "I had a clear and long-running fantasy of being some kind of loosely defined royalty, a mysterious European princess; but I was also a detective in a mackintosh. We didn't have comics or a television in the house, so it must have come from the movies. We had family outings to the cinema every week. I must have started going when I was very small, because I remember taking my teddy bear along in a shopping bag."
A later, and still-running fantasy, was to play a chanteuse on stage, "like that woman, what's her name, lying on top of the piano - Michelle Pfeiffer [in The Fabulous Baker Boys]. At some point you just have to open your mouth and let it out. It's all part of a fantasy about letting go." But can she actually sing? She smiled sweetly. "Only under hypnotherapy."
Many people wonder how it was that Lindsay Duncan appeared as from nowhere in her mid-thirties, in Les Liaisons Dangereuses, reasoning that such an obvious star could not have gone unnoticed all through her twenties. Where had she been? She bridled a little. "It's no great mystery. I didn't get to drama school until I was 21, I did lots of weekly rep, I spent a chunk of time at the Royal Exchange, Manchester, when it opened, and I was doing great plays like Top Girls [by Caryl Churchill] at the Royal Court, which isn't exactly off the map..."
Her favourite memories, however, are of weekly rep, which she speaks of with gurgles of pleasure: "Ah, summer rep in Southwold. It was so completely different from drama school, where you'd sit lolling about in ladies' changing rooms talking about cottage cheese and dieting and sex, and not doing enough work, and being too stoned to read books. To go into weekly rep is like `Go!' - it's a terribly speedy lifestyle. Because you do a different play every week, you have to work on the next week's play all day, then perform at night, then learn your lines after the pub - I don't know how, but when you're young you can do that - and you sew sofa covers because you are, after all, the acting ASM..."
What were the plays like? "Oh - French Without Tears, safe and popular stuff. Some of it was absolutely ghastly, Agatha Christie, detective plays. I remember one called Public Mischief - terrible stuff, recycled all the time. But in those days you were so excited about getting your Equity card, you'd do Agatha Christie until your eyes crossed to get the f***ing card." She pulled a stray blonde hank, reminiscently. "And also it was summer, and it was so mad - we were sleeping in the dormitory of a boys' public school, in this quaint little English seaside town locked somewhere between the Thirties and the Fifties. It was... heaven."
Goodness. The sight of Ms Duncan in ecstasy is a most appealing one. And she has a way of slowing down her speech to a languorous crawl just this side of silence. (She enunciates the word "sex" as if entranced by the sound it makes: "seck... [two-second pause] ... ss.") It is perhaps the suggestion of sensuous appetite behind the regal sophistication that is her most potent weapon. Had she, by any chance, fallen in love with her director? She laughed with delight. "Hardly. The place was run by Sam, a Cambridge don who padded around in his plimmies, very stiff in the joints, seemed about a hundred to me, and his wife Joan, who was an actress manquee. Every summer they came over from Cambridge and ran Southwold rep. She got all the leading parts in her age range and he directed her. Me, I had a completely obvious affair with another actor. It was a great summer. What else did you want?"
When she hit the big time, life speeded up. Top Girls took her to New York and Joseph Papp's Public Theatre when she was 31, the Royal Shakespeare Company took her on (she played Helen of Troy in Troilus and Cressida at Stratford), then the National Theatre, movies, television. She managed to survive a critical mauling that would have sent other actresses into permanent exile, when the BBC launched their misconceived A Year in Provence: "Pointless, witless, hopeless and useless" was one of the more positive judgements. When she starred as Anna, the Rector's Wife who gets a job stacking supermarket shelves as a blow for independence, you could feel the breath of middle England - all those super-protective Joanna Trollope fans - on her neck. "I had clergy wives who wanted to talk to me about it. They said, `Don't let them soften it.' I've never been involved in anything before where people approach you because they worry about how it's going to be done. So much for all the intellectual snobbery about Joanna Trollope. She's obviously got a direct line to an awful lot of people."
And now she's back in Pinter country, playing the Vivien Merchant role in the great playwright's 1965 domestic nightmare. "I couldn't have borne it, finishing Ashes," said Ms Duncan theatrically, "if I hadn't known I was doing The Homecoming. I'd have been terribly depressed and bereft. Pinter has this unmistakeable voice - it's such a familiar landscape to me, it carries the ring of absolute authenticity. I just believe in his route through people."
Authenticity, eh? The Homecoming, like many a Pinter drama, starts naturalistically, but sheers off into surreal and unsettling territory. Its thirtysomething young couple, Ruth (Duncan) and Teddy (Keith Allen), arrive back from America at Teddy's family home, where his querulous, bullying father rules a spectacularly nasty roost and his brothers, Lenny and Joey, move in on his wife like rutting dogs. Ruth herself changes from nervous wife into sexual predator, apparently with designs on both brothers, if not the whole household. The men discuss her openly as a "scrubber" and "slut" and, by the time the curtain falls, Teddy has gone and Ruth remains - though whether as sex, slave, housekeeper or dominatrix, is never clear.
Was it clear to her? Ms Duncan turned a slightly pitying smile towards me. "Not only do I understand it, I can't think of anything that makes more sense to me. I expect I'll have a lorryload of crap dumped on my head when the play opens, but I feel completely at home with it."
What did she think it was about? "It seems to me the whole play is about people fighting for their territory. It's what happens in families. It's clear how the men go about their business with each other, so the arrival of a woman is both desirable and threatening. But she badly needs some territory herself - she's got this husband and three children, three American children, and when she comes to this place, she sniffs the possibility of getting some territory to call her own. That's why I don't think of her as a seductress. I see her as using her sexuality as a means of survival. It's the missing ingredient in that household. And the play's about that curious interdependence which we all share and we all try to wriggle out of, but we can't. She needs them and they need her and the degree of dependency will vary all the time."
Did she find all the misogynistic rant a bit tiring? "But the hostility is an indicator," she said patiently, like a psychology lecturer. "You don't go around speaking to people as Lenny does unless you're slightly nervous of them. And it raises all those questions about how tidy our lives are - about what you're likely to find behind any front door..."
Ms Duncan's critique of her new role is so unexpectedly fluent, one wishes she could be persuaded to unbutton to the same degree about her likes and dislikes. Talking about how she compares with, say, Vivien Merchant for radiating creepiness, she said she prefers complicated characters ("So that, even if they're wielding a cleaver, you still can't miss their vulnerability"), and I asked if she'd like to go really over the top one day - like, say, Glenn Close... The effect was electric. Ms Duncan's face positively contorted at the mention of the actress who played the Marquise de Merteuil (the part that Duncan had made her own) in the film of Liaisons. "Did you actually see the 101 Dalmatians?" she asked through her teeth. "Yes, yes," I said. "It was jolly good. I thought Ms Close in particular was..." "You're definitely entering Don't Quote Me territory here," said Ms Duncan severely, and would not be drawn into further indiscretion. We ended in a fusillade of praise of Harold Pinter, with whom she clearly enjoys a passionate mutual admiration: "He has this fantastic degree of concentration, this rigorous intelligence, and he doesn't blether on. He doesn't waste words or time. And he's always for you."
The brittle, queenly Ms Duncan, low- status background long behind her, high- status career intact, made to leave. Such a curious blend of coolness and passion, warmth and aloofness. Some distant memory of The Rector's Wife made me ask: do you possess an Aga? "No I don't," said Lindsay Duncan shortly, "and I'm not looking for one. I'm more a stainless steel sort of girl."