Doris Lessing can be fierce. But this morning, as you might expect from an 88-year-old woman who has just been awarded the world's highest literary accolade, she is all smiles and kisses. The stairs of her ramshackle terraced house in West Hampstead are lined with bouquets of flowers. The upstairs living room, which I remember from the last time I interviewed her as slightly gloomy, crowded with towers of books and magazines and oppressive paintings and wall hangings, is today brightened by yet more flowers, all in deep shades of orange and red. "People obviously associate me with sunset," she says. Her cat is in a sulk, she says, because he hasn't been getting enough attention because of all the fuss. Yet despite the commotion of the past 24 hours we are alone, though the telephone, set to a piercing shrill - she is going slightly deaf - rings constantly with congratulations. The best, she says with unconcealed glee, was a call from her hero Gabriel Garcia Marquez. "I've been terribly touched by the range of people who are pleased for me."
So this year's favourite, Philip Roth (the odds were 7/2), a wildly prolific, controversial grand old man of literature famous for writing about masturbation, politics and male neurosis has been beaten by the outsider (at 50/1) a wildly prolific, controversial, grand old lady of literature famous for writing about menstruation, politics and female neurosis. She is, as all the reports have noted, only the 11th woman to have won in the prize's 104 years. So is this a triumph for female writers? "I hate talking about literature in terms of men and women. It isn't helpful." But she is very sorry Virginia Woolf was never on the list.
One of the reasons, perhaps, why Lessing is not such surprising choice is that she is above all a novelist of ideas and idealism. Post-colonialism, communism, feminism, mysticism - there are few 20th-century -isms Lessing hasn't been tagged on to, wittingly or otherwise. "They - she says waving - they out there, they like to have labels it makes it easier."
The literary critic Harold Bloom has called the academy's decision "pure political correctness", I say. "Harold who?" "Bloom". "Oh, Harold Bloom. What does he mean, do you think? Maybe he thinks it's time they gave it to a woman." The phone rings again. "Tell Harold Bloom, I've had much posher recommendations," she says, chuckling.
So why does she think, after 40 years of being shortlisted, she got it? "It is probably because I have written in so many different ways, with never a thought that I didn't have the right to. It is an impressive list."
Would she have felt disappointed, if she had never won it? "No, it has been going on for years and years, honestly, it was so boring. I've won all the European prizes. This is the most glamorous one, but it doesn't mean to say it is the best from a literary point of view."
She was once asked to become a dame of the British empire, but was reported to have said to have turned it down because it was "a bit pantomimey". Did she really say that? "Yes, I did," she says, rocking back on a sofa so low we are almost squatting on the floor. "Well, first of all there is no British empire, no one seems to notice this. Then they said would I like to be a companion. A companion to whom or of what? Honestly."
She is undoubtedly Britain's elder stateswoman of feminism - a mantle she has been trying to shake off since The Golden Notebook was proclaimed "a feminist bible" in 1962. Does she really, as she has said, see the novel as her "albatross"?
"This book has got a sort of charge to it. I have to recognise it. It keeps popping up somewhere in some other country and I have to say 'My God, this book has got something.' It has got a quality, a vitality."
Her fellow laureate JM Coetzee has called her "one of the great visionary novelists of our time". And something often overlooked about Lessing is that she has been as much a pioneer of form as of ideas, her fiction evolving from the humanist-realism of her early novels to her fantastical middle phase. With characteristic contrariness, she is most proud of her Canopus sci-fi series, which left many critics bewildered. "I think some of my best writing is in that Shikasta series. They are experiments. The trouble is we should never underestimate the conservatism of the literati ... When The Golden Notebook came out nobody noticed that it was quite an interesting form I was using, they were much too obsessed by the fact that I was meant to be anti-male, this ball-breaker."
She seems to have fun in baiting the sisterhood with an unashamedly un-PC avowal of biological determinism and the intrinsic difference between the sexes. Her last novel, The Cleft, a dystopian fantasy that depicted the female sex - the eponymous "clefts" - as lumpen and lazy, but handy with a broom, and the men as inquisitive, adventurous "squirts", left some female critics spluttering.
As with WH Auden, the beautiful portraits of Lessing in her later years have made her one of literature's most recognisable faces. With its time-and-expression worn lines and far-reaching eyes, her face gives the impression of a lifetime of staring out across the African veld - which in a sense is exactly what she has been doing ever since leaving Johannesburg in 1950, with her first manuscript in her bag.
Lessing's own story will be well-known to her readers, not least because she has spent many years chronicling it. In her memoirs she describes with an almost obscene intimacy the sights, sounds and most potently the smells of the African bush that nurtured and formed her. Her childhood - split between a boisterous outdoorsiness and an intense inner life - was dominated by her overbearing mother, with whom she fought "steadily but reluctantly" until her death. Although mother-figures loom large in her fiction, it is only recently that she has been able to write about her directly. Has she forgiven her? "I have explained her, if that is forgiveness."
Her latest novel - which she claims might be her last and which she has just delivered to her agent - is called Alfred and Emily, after her parents. She has always described them as crippled by the first world war (her father physically: he lost a leg; her mother emotionally). In the first half of the novel, she has "abolished world war one for them so they have ordinary, decent quite plodding lives". The second half tells what happened after they moved to Southern Rhodesia. "Basically, it is an anti-war book, which is not what I set out to write." Was she influenced in this by current world events? "No, not really. I hate war of course, I think a lot of young people have no idea what war was like. I'm horribly afraid young people might see war as glamorous."
She has said that the English are best at "small, circumscribed novels, preferably about the nuances of class or social behaviour". "That's true. They do it supremely well." Does she think the contemporary novel should engage in politics more? "No, you might be surprised by this, but I've never thought a novel should be a political message: look through my work and find a novel that is a political message."
So what does she think is her greatest achievement? "What I have done is go on writing through thick and thin. I've stuck at it. Sometimes it has been quite difficult. Don't forget I had a child through the early part of this." One of the other most remarked-upon features of Lessing's life is that, along with Muriel Spark, who unbeknown to her at the time lived nearby in Rhodesia, she is one of literature's most famous bolters - something for which she has been given a hard time, for refusing to demonstrate insufficient breastbeating. "Muriel's child was looked after by grandparents and my children were looked after by a second wife. They weren't exactly abandoned on a doorstep."
Didn't she feel terribly guilty? "No, you see, that is the difficult thing. Because if I hadn't left I know what would have happened to me. I would have had a massive nervous breakdown and become an alcoholic. While it was a terrible thing to do, it was right to do it."
But there is a sad irony in the fact that Lessing has spent the past few years caring for her middle-aged son by her second marriage, Peter, who lives in the adjoining flat. He has been very sick and in hospital a couple of times, and it has become increasingly difficult for her to find the time and energy to write.
While many authors will claim they write entirely for themselves, one feels with Lessing that this is true. She writes about what she is interested in at that moment, and if readers don't like it they can just lump it. And those readers who do, don't just like her, they love her.
"It is wonderful," she says. "I've met girls who say 'My mother told me to read you, and my grandmother.' That is really something, isn't it?"
