Depression, fame and Hollywood - after 30 million books and £15 million, the reclusive J. K. Rowling opens up.]Joanne Kathleen Rowling does not do anything by half. For months she has been writing, writing, writing - up to ten hours a day - to finish the fourth Harry Potter book. Now she is in recovery mode and giving her first interview for a long time. I say that I have heard that she has become a recluse and hates interviews. She gives me a look as if to say don't believe everything you read. Then she launches into the interview like a bat out of hell.

She talks so fast that it is just possible she has found a way to avoid breathing altogether. The only time I see her inhale is around a Marlboro Light. She claims this was to be a non-smoking day. I'm not sure how this squares with five cigarettes in two hours. She is hyped up, helter skelter and is serious and funny at the same time. "We've been everywhere!" she exclaims at the end. "We've done jewellery, we've done depression." She laughs, puffing away. Clearly the recluse phase is over.

We have met once before, two years ago, when she was 32 [link]. Neither she nor Harry was famous then and we sat at the long, imposing table in the library at Bloomsbury Publishers in Central London while her four year old child Jessica played with a Hercules doll and demanded to be taken to the loo.

Rowling was thrilled that Harry Potter had sold 30,000 copies. "I never dreamed this would happen. My realistic side had allowed me to think I might get one good review in a national newspaper. That was my idea of a peak."

Well, there are peaks and then there are the Himalayas and for the past two years Rowling has been travelling with the sherpas pretty much full time. The Harry Potter books have sold more than 30 million copies worldwide and been translated into 31 languages. They totalled 98 weeks on The New York Times bestseller list and in Britain last year occupied three of the top five slots. Harry has been on the cover of Time, and Rowling has been accused of plagiarism, always a sign you have arrived. And there is a film, which means that she really is lunching in Hollywood these days. Next Saturday sees the launch of the fourth book, Harry Potter and the Goblet of Fire, which at 640 pages is one of the biggest children's books of all time.

Exhausted? Well, you would be if you had to witness the negotiations between Bloomsbury and my bosses for this interview. In fact, there were initial signs that Rowling had become rather grand. She was now the kind of person who has "people", as in "my people will talk to your people". And rumour was that she had become "a bit of a madam". Certainly she had broken the news barrier; every other day there is something about her in the papers.

So I expected her to arrive at the Edinburgh hotel for the interview with at least a smallish entourage, if not dark glasses and a lapdog. In fact, I went to the foyer to look for just such a person only to stumble over someone else. She was short (5ft 4in) and grinning. On closer inspection it was Rowling. "It's the hair," she says. Indeed, the hair that had been long and dark is shorter and lighter. But it is not the hair. It is the fact that she has failed to acquire that burnished sleekness that is the preserve of the rich and famous. In short - and this is not meant to be rude, just informative - she looks like one of us.

Joanne Rowling is no good at small talk. In fact, there is a chance she is incapable of it. Within minutes of sitting down she is talking about death and fate. She is intense and animated and, really, you do have to concentrate to keep up. I try to find a pat answer but give up after a while.

Perhaps the problem is that everyone thinks of Rowling's life as a fairytale and, in many ways, it has been. In 1993 she was indeed a poor single mum who had left her new husband back in Portugal. She did write much of Harry Potter at an Edinburgh café while she nursed an espresso for two hours (minimum) as Jessica slept in her pushchair. She did send it off to an agent who said, yes, thank you very much. And now, of course, she is rich and famous and in the Himalayas.

Yet Rowling concentrates not on the fairytale but on what came immediately before. The fact that she has been seriously depressed and desperately short of money are defining factors for her. She is also aware that without that failed marriage in 1993, there would be no Jessica and possibly no Harry. Life does not come in a neat package, I say, and she pounces on this. "People do want life to be neat. That is undoubtedly true. But you know the four great truths of Buddha: the first one is 'Life is Suffering'. I love that. I LOVE THAT. Because I think YES. Life is not supposed to be neat. And it's a comfort. It's a comfort to all of us who have messed up. And then you find your way back, bizarrely. And I'm sure to mess up again at some point - though, I hope, not on such a grand scale."

Can she believe what has happened to her? Does she ever wake up and say I cannot believe it?

"Pretty much every morning."

Well, I say (getting into this word emphasis thing), it IS unbelievable. "Hmm, it has overshot the mark. I remember thinking during book two that we had reached saturation level but then, with the next one, The Prisoner of Azkaban, everything exploded. I mean exploded. I could not believe it. I could not." What does she mean? "Well, I mean that it was on The Nine O'Clock News! Call me naive but that wasn't anything that I expected. And then newspapers which shall remain nameless started banging on my door. I never expected to be doorstepped. It kept happening and I hated it. And then stuff starts appearing in the press that is untrue. And then you really start getting a taste of what happens to those I would always consider proper famous people."

She says that she knew it only be a matter of time before they found her former husband, a journalist whom she met in Portugal while she was teaching English. "I married on October 16, 1992. I left on November 17, 1993. So that was the duration of what I considered to be the marriage." So what happened exactly? "I never talk about that. But obviously you do not leave a marriage after that very short period of time unless there are serious problems. I'm not the kind of person who bales out without there being serious problems. My relationship before that lasted seven years. I'm a long-term girl. And I had a baby with this man. But it didn't work. And it was clear to me that it was time to go and so I went. I never regretted it. So I thought they would go for him and they did."

So who, exactly, are they? Rowling, who never says one sentence if 25 will do, embarks with relish on a story. "OK, I'll tell you. On the Sunday that this interview appeared I did not have a clue what had happened. The phone rang at about am and it was a friend. He said 'Are you OK?' I said 'I'm fine, how are you?' "He said 'Oh, you are doing OK then?'

"He was talking to me like I had just had major surgery. So I said 'Shouldn't I be OK?' "He then said 'Oh my God, you don't know'. " She says that he then tried everything to get off the phone. "Eventually he did tell me and all I could think of to say to him was 'What WERE you doing reading Mail on Sunday!?' And he completely lost it. He went, 'Uhhh, someone left it behind in the café!' Anyway, what can you do? It's done. In a way it was a relief. I knew it would happen. Once it's done, it's done."

But it is not really that simple. Rowling says she no longer reads what is written about her, though I'm not sure I believe her. A friend convinced her to read a piece last year, saying it would make her laugh. "It said I had become irascible, irritable, paranoid about protecting my privacy and never wanted to give interviews because success had turned me into some sort of Howard Hughes figure."

I check her fingernails. Not long enough, I say. "Actually it wasn't Howard Hughes. It was more like children's literature's answer to Salinger. You know, 'Darling I want to be left alone with my art!' And it did make me laugh. I have to laugh because day to day I lead an extremely ordinary life in terms of what I do and where I go. Very mundane."

Mundane? But she is now worth a lot of money. (Forbes magazine's rich list has put her book earnings at £15 million).

"Yes, I have got more money than I ever dreamt I would have. Great! I have stopped worrying about money. For a few years there I really worried about money. I lived with it like it was a person living with me."

But, I ask, aren't you going to buy something, like a yacht perhaps? This makes her bark with laughter. Rowling says that, like any girl, she likes to go shopping. Then she looks down at her jeans. "I saw you look at my jeans and think 'Why don't you go shopping!" But, I persist, most people in your position would have bought something by now.

Then, suddenly, she deviates from her script on this subject (I know this because she announces that she is) and embarks on another story. "OK, it was about a week after my ex-husband had sold his story. Then there was a story that was totally fabricated. Nobody had printed an entire article that been fabricated before. I know, I know, but I'm a virgin to this business, you know? If that story hadn't appeared the previous week, I'm sure I would have been 'OK, you can lie about me but I know it's not true'. But I was in a weakened state."

You were vulnerable, I say.

"I was VERY vulnerable at that point. Then, as usual, the worst sign that I am upset and it really doesn't happen that often I couldn't write. I went out that day intending to write. I went to a café and just sat there doodling; I couldn't do it. That made me even more depressed. I thought, now they've attacked the one thing that was really constant. Now I can't write! Great! So I was walking down Princes Street and thinking 'What shall I do?' and then I just thought 'I know, I will go and spend a lot of money on something I really want'. I went into a jeweller's and bought this ring. It was the first time in my life that I bought something that I knew was expensive without asking the price. I think the jeweller thought I was a nutter."

I ask the obvious question: diamonds?

"Aquamarine," she says with satisfaction. "A big one. I had it altered and when I got it back I said 'This is my Statement Ring, my No One Is Grinding Me Down Ring'. A friend said 'Let's face it, you could give someone a hell of a scar if you hit them. It really is a knuckle-duster'."

Joanne Rowling was born in Chipping Sodbury General Hospital in July 1965. Her father was an apprentice engineer at Rolls-Royce who worked on aircraft engines, her mother was part French and part Scottish. Her parents met at the age of 19 on a train as it left King's Cross - Rowling claims it is the most romantic station in the world and married at 20. Rowling was born nine months later and then came her sister Di. They lived in Yate, outside Bristol and then Winterbourne - it was here, on a street of semi-detached houses, that she lived four doors away from the Potters. She stole their name, as she has stolen so many others, because she is a word magpie. She especially loves strange names. Chipping Sodbury makes her chortle and it cannot be the first time that she's said it. Later, while taking her photograph in the Royal Botanic Garden in Edinburgh, she is thrilled to find a plant name plate that says Bogbean.

It is impossible to talk to Rowling about her childhood without also talking about Harry Potter and his life at Hogwarts School of Witchcraft and Wizardry. Part of this is because she has ransacked bits of her past and given them to Harry and his friends, Hermione and Ron. But part of this also is that Rowling spends a lot of time inside Harry's world, and it is real to her. Every character has a family tree, a psyche, even dietary requirements. She's in charge, so she knows their futures, but doesn't let much slip. She likes secrets. She came up with the idea for Harry Potter on a delayed train and knew from the beginning there would be seven books - one for every year he is at boarding school - and she wrote the final chapter of book seven years ago. It was hanging around the house for ages before she realised it should be put somewhere safe. What, like a bank? "No, safer than that."

The character of Hermione is Rowling as a young girl: hard working, bookish, a worrywort. Rowling says she was painfully swotty, with NHS spectacles and short, short hair. She claims that she loosened up a bit later on but I'm not so sure about this. At times during the interview she is nothing short of earnest, especially about her work. She defends Hermione pretty fiercely, too. "My American editor says that I am mean to her because she is me. But I don't think that I am mean to her. I love her dearly."

But, I say, Hermione tries so damn hard. In Harry Potter and The Prisoner of Azkaban, for instance, she looks into the mirror that reflects what you fear most and sees a teacher telling her she failed all her exams. "I understand where that is coming from. It comes from believing yourself to be plain and feeling yourself to be no good at anything else so you've got to achieve something. I completely understand Hermione and I really love her and I don't want to depict her as a feisty little ..."

She breaks off and then starts to mutter. "It irritates me. It irritates me. What irritates me is that I am constantly, increasingly, being asked 'Can we have a strong female character, please?' Like they are ordering a side order of chips. I am thinking 'Isn't Hermione strong enough for you?' She is the most brilliant of the three and they need her. Harry needs her badly.

"But my hero is a boy and at the age he has been girls simply do not figure that much. Increasingly, they do. But, at 11, I think it would be extremely contrived to throw in a couple of feisty, gorgeous, brilliant-at-maths and great-at-fixing-cars girls."

This is the kind of speech that makes you want to clap and, really, I don't think that Rowling was talking to me, per se, here. So has there been pressure from the film people to change the characters? Make them more American? Make them, well, just a bit feisty?

"At the moment, in all honesty, they don't. Maybe they did in the beginning but then they saw the popularity of the books as they are. At the moment they are giving me a huge amount of influence. It will be filmed in Britain, with an all-British cast."

Did she insist on this?

"Well, I made loud noises."

Christopher Columbus is going to be the director and is moving his family here for the job. But Steven Spielberg had been involved at some point. Did she have a fight with Spielberg?

"No."

Did she speak to him?

"I have spoken to Steven Spielberg. Did I have a fight with him? No, I definitely did not. I read that in an article and was mystified. There were things he said that I didn't agree with, there were things he said that I did agree with. Let's just put it this way: I am very happy with the director we've got."

So what about merchandising? Can we expect little Harry Potter dolls in the future? Rowling looks pained. "Well, uh, Warner Brothers is perfectly aware that this is the area that I am most concerned and worried about. I can't lie about it."

She likes the idea of games or dressing-up clothes, but I was actually thinking of those plastic figures that come with McDonald's Happy Meals. "We have to be honest about this. People ask me if there will be merchandising. Well, name me a children's film that doesn't have it. That's a given. That is how the film company makes its money."

But kids like to have something to play with, too, I say. "The brutal truth is that yes, they do. But they wanted the books most and they wanted the books first, so maybe we should all hold on to that and then do what we can to make sure that the film is as true as possible to the books."

So, have you had to stick to her guns at any point? Rowling's voice grows soft. "I have stuck to my guns all the way through." And then she laughs.

But, I say, you couldn't have hated it too much: you were head girl. "Yes, but you don't know the comprehensive. Trust me. It was like being voted Least Likely to Go to Jail." Rowling duly got her A levels in French, German and English and went to Exeter University. She then did a series of secretarial jobs rather badly (or so she says). One was at a publisher's, where she was in charge of sending out rejection letters.

The only thing that she ever really wanted to do was write. She had always been a secret scribbler - her first story, called Rabbit, was written at the age of six - but never finished anything. She started writing the first Harry Potter book in 1990. At the time she was employed, happy in a long term relationship, living in London. Then her mother died from multiple sclerosis at the age of 45 and suddenly Rowling's life just went wrong. Before she knew it, she was a poor, single mum living in a grotty, cold flat in Edinburgh with only two friends to her name and nothing to do but write.

People talk about the Harry Potter books as wizard wheezes but they have a pronounced dark side as well. The Dementors, for instance, are prison guards who track people by sensing their emotions. They disable their victims by sucking out all positive thoughts and with a kiss they can take a soul while leaving the body alive.

I do not think that these are just characters. I think they are a description of depression. "Yes. That is exactly what they are," she says. "It was entirely conscious. And entirely from my own experience. Depression is the most unpleasant thing I have ever experienced."

What does she mean?

"It is that absence of being able to envisage that you will ever be cheerful again. The absence of hope. That very deadened feeling, which is so very different from feeling sad. Sad hurts but it's a healthy feeling. It's a necessary thing to feel. Depression is very different."

Now, in Harry Potter and The Goblet of Fire, death comes for us, too. The identity of the corpse is secret until next Saturday, though she will say that it is a character we care about.

"Yes, this is the book in which the deaths start. I always planned it this way. It's become a bit of an idée fixe with me. I have to follow it just the way I wanted to write it and no one is going to knock me off course. If it's done right, I think it will be upsetting but it's not going to be damaging. I have said from the beginning that if you really are honestly going to examine evil actions then you have a moral obligation not to fudge the issue."

Goblet of Fire has been a trial. She had written half of it when she discovered a "gaping hole" in the plot. This had never happened before. Rowling likes to worry: if there is nothing immediately to hand to worry about, she will invent something. But here was something real. "It's the central book. It's pivotal in every sense. I had to get it right."

Some days she wrote morning, noon and night. She is happy with the end result. But, I say, 640 pages! I mean, the first book was 223, the second 251 and the third 317. It is all getting rather out of hand. Rowling looks a bit embarrassed. "I know. I was shocked to see how long it was."

Her day-to-day life, as she describes it, is completely lacking in glamour. She takes Jessica to school and spends the morning at home with her PA dealing with the "800 things that come in". She receives a huge number of letters from children. All are answered, some by hand. In the afternoon she goes out to a cafe to write - working at home is oppressive - and then returns home to make tea. The evening is spent procrastinating and wandering around her house.

Harry Potter is full of wonderful creatures: owls that deliver post, cats that can sense a lie, unicorns with silvery blood. But Rowling is not so keen on her own. The guinea pig used be at her daughter's nursery. "I was the only parent mug enough to say that we would give it a home. Then, because I am this earnest person, I thought that it was not fair for it to live on its own. So I bought this rabbit. I had anticipated that it would be this cute fluffy little thing. No. It is vicious. Absolutely vicious. It was sold to me as a dwarf and it's now the size of a hare. It's jet black. It attacks.

"I had these great gouge marks on my wrist from it and I gave an interview with these gouge marks and I thought this guy was thinking: Now she's really cracking up under the pressure. I'm like 'No, it's the rabbit'."

Either Joanne Rowling is a great actress or she really has not succumbed to the disease of celebrity. I listen for a name drop and it does not come. I listen for references to money and she does not make them. Her publisher may play the secrecy and hype game with the best of them but somehow Rowling manages to remove herself from this madness. She sees herself as a writer and, for her, that is that for the time being. And the future? She gets a lot of requests from charities and says she is tempted.

Rowling: "The trouble is, will people still be interested in me after I've finished my writing? Until Book Seven is finished, my priority has to be the books. At which point I will become ..."

Me: "Even more rich and famous."

Rowling: "That wasn't what I was going to say. I was going to say at which point I will fade back into blissful obscurity."

Me: "I think not."

Rowling: "Well, I think so."

Me: "No, not blissful obscurity."

Rowling: "No, you don't know. It will be."