During a massive event in July 2000 to celebrate the launch of Harry Potter and the Goblet of Fire, Newsround's Lizo Mzimba boarded the Hogwarts Express to talk with JK Rowling.

The interview is in four parts.

JK interview Part 1 - Fans and the four books

So King's Cross, amazing reception, what was it like?
JKR: It was the best - all those children, it was wonderful.

Is this the best part of doing the publicity for a book like this, actually travelling round the country meeting people?
JKR: My favourite thing's the writing and then when you have to do the odd promotional bits meeting the children is by far my favourite thing - it's wonderful. And the not so young children.

What's the weirdest thing a child's ever asked you at an event or promotion?
JKR: The most startling thing or things I've ever been asked are when children ask me questions that reveal that they are clearly following my thought processes a lot more closely than I would have guessed.

There was - I can say this now because book three's out - a boy asked me in San Francisco: "Where did Scabbers come from, what's Scabbers' history?" And Scabbers, for people who don't know, is a rat who subsequently was revealed not to be a rat at all and I found it quite spooky that he homed in on Scabbers because, of course, I'd known from the first book that Scabbers wasn't really a rat.

That kind of thing keeps cropping up and I think the thing is that children are reading them 12 times, or whatever it might be, and they really are starting to know the way my mind works.

Is that a danger with the Internet as well - you've got this community that ...
JKR: Twice I've been on the Internet. Friends of mine were telling me what was on there and I'd never gone looking. The first time I went in there I thought I'm never coming back because it's too scary because some of the stuff that's out there is very weird.

The second time I went in there I was looking for something specific, someone had set up an unofficial fan site where you could be sorted - they had the sorting hat and you could be sorted into a house, so I was Hufflepuff. I wasn't that pleased - obviously I'm supposed to be Gryffindor, if anyone's Gryffindor I'm supposed to be Gryffindor.

Do you find it's a worry that you can say one thing in a conversation somewhere, say something else in an interview somewhere, and people will put all these facts together and draw conclusions that are eerily close to what you're going to do in the books?
JKR: Mostly what's happened is that people have put together something I've said, something they like to think I said, something someone else said - which is completely false - and drawn completely the wrong conclusions. That's inevitable, that just happens. But no one yet has guessed what's going to happen or come anywhere close in fact.

Now book four, I finished it - early hours of the morning - very scary ending.
JKR: It is very scary isn't it? I think it's very scary.

How difficult was it to write that?
JKR: The first time ever I cried while writing - I actually cried twice during the writing of the ending of book four. Basically it's a powerful ending but as you well know from reading it there's a reason why it has to be that powerful, something very important happens at the end of book four, very important.

And having said all along that if you are writing about evil I believe that you should give children - you should have enough respect for them to show what that means, not to dress up as a pantomime villain and say - lots of smoke and thunder, I think, and it's not frightening at all really.

So I can only say that that's the ending I planned and I think it came off okay. I was very happy with it when I reread it, although bits of it made me cry.

Do you rewrite a lot and was it a difficult?
JKR: A huge amount. Once ever in the four books that are published I've sat down written something beginning to end and let it stand and that was in the chapter in the Philosopher's Stone where Harry learns to fly.

I remember vividly the afternoon, my daughter fell asleep I ran into the café on a beautifully sunny day, I sat down and I wrote that chapter from beginning to end and I think I changed two words and that's very unusual for me.

There's a chapter in book four I rewrote 13 times and at one point I thought the book will never happen if I keep rewriting chapter whatever it was.

And how vital is book four in the whole seven book series to Harry?
JKR: Crucial. The fourth is a very, very important book. Well you know because you read it, something incredibly important happens in book four and also it's literally a central book, it's almost the heart of the series, and it's pivotal. It's very difficult to talk about and I can't wait for the day someone's read all seven and I can talk completely freely about it. But it's a very, very important book.

What was it like with all the pressure? I know you write for yourself very much so, rather than to a target audience but it must have some effect - the expectation and pressure that's built up over the last year around Harry.
JKR: Actually the expectation doesn't bother me at all because I think my readers are just sort of thinking well they want to hear the story that I want to write. So I feel that they just want to find out what happens next and my version is the version they want to hear. So I'm kind of confident about that.

But there are other pressures dependent on having a very successful book which I have obviously got with the third book, that was difficult. But the weight of expectation from readers, no it doesn't particularly bother me.

JK interview Part 2 - Themes and tales

Book four explores a lot of themes, some we've seen before in Chambers of Secrets, about prejudice. Is that something you've been wanting to explore?
JKR: From the beginning of the Philosopher's Stone prejudice is a very strong theme - and I think it's plausible that Harry enters the world - that's how I wanted it to be - he was quite wide-eyed about it, everything will be wonderful in this world, this is the place where those sort of injustices didn't happen and then he finds out that sure enough it happens.

And it's a shock to him like to everyone else and he finds out that he's a half person within the confines of the world. To a wizard like Lucius Malfoy, Harry will never be a true wizard because his mother was of muggle parentage.

So this is a very important theme and I always knew - well obviously I knew I've been trying to do it for 10 years now - yes so that becomes stronger and stronger.

Well I think it is often the case that the biggest bullies take what they know to be their own defects, as they see it, and they put them right on someone else and then they try and destroy the other and that's what Voldemort does.

And that was very conscious - I wanted to create a villain, where you could understand the workings of that person's mind.

And Harry, as you know, from book four, is starting to come to terms with what makes a person turn that way. Because they took wrong choices, and Voldemort took wrong choices from a very early age - he decided young what he wanted to be.

Was it difficult balancing the light and dark in the book? You've got some very dark moments and some wonderful moments of humour - talking about Mad-Eye Moody, the man who can't tell the difference between a handshake and attempted murder and a slightly dodgy joke about one of the planets in the solar system.
JKR: Yeah it is slightly dodgy. I was surprised my agent let me get away with that actually because as I wrote it I thought she's going to pull this book but she really laughed at it, so she let it stand.

Is it difficult? No because my experience is in a very limited way that even when life is really not that bright people still laugh in the most tragic of situations, people still laugh.

And the ending of the book is actually very important to me because, as you know, Harry says - We're going to meet the past - that's what's so admirable about human beings that even when they are really against it, when they are really in the direst of situations there is still humour, there just is, you will find that almost everywhere, so that's quite important to me.

Why was it important to show some of the strange friendships developing in this book?
JKR: Well in book four, for me, Harry, Ron and Hermione, all of them, are really starting to find their own identities and that means, in their various ways, facing up to the things that have been imposed on them by their parents or school.

For Harry that's facing up to his fame, really facing up to it for the first time because he's been put into this situation where he will, for the first time, really get the weight of outside interest. So that's scary.

Ron has to deal with his jealousy - he's made friends with the most famous boy in his year and that's not easy, it's not easy to be in that situation. And Hermione gets a political conscience. Hey!

Is this your idea of Hermione lightening up as you've said before?
JKR: No, she will.

She didn't seem that light to me she was quite radical.
JKR: Yeah, she's a good girl Hermione. I agree with you she's not that light in this book but people made the mistake - when I was writing book four - of assuming that my answers related to book four, there are another three books to go.

But in some ways Hermione has - she's more of a rule breaker now, where her convictions are concerned she's prepared to do stuff that she's really not supposed to. So, in that sense, she will lighten up, I promise you, I did in the end.

Last time I spoke to you there was another Weasley coming in this book....
JKR: I know I'm sorry about that. What happened on book four and one of the reasons why it was easily the most difficult to write, which had absolutely nothing to do with Harry being famous or me being famous or anything like that, the first time my plan fell down ...

The famous plot hole. I got halfway through my plans and realised there was this huge gaping hole in it, there's two - it just didn't meet and that was entirely my own fault, I should have had the good sense to go through it very, very carefully before I started writing but I hadn't.

So I'd written what I then thought was half the book it turns out to have been a third of the book before I realised that this wasn't going to work, so I had to do an enormous amount of unpicking, and in the unpicking process I'm afraid the Weasley got [draws finger across her throat] ...

Will we be seeing her again?
JKR: It's possible, I really like her as a character but with my plot being quite intricate in the context of what I'm dealing with I'm not sure that she'll fit anywhere else, so she'll be the character that might have been.

JK interview Part 3 - ideas and inspiration

It's quite appropriate we're talking to you on a train, it's very important in the story.
JKR: Yeah I love trains. I wouldn't be here if it wasn't for the fact that my father managed, by the skin of his teeth, to get the train from King's Cross - that's where he met my mother. He proposed to my mother on a train, I had the idea for Harry Potter on a train, yes, very appropriate, I love trains.

Do you sometimes get a bit tired of people saying to you where did the idea of Harry come from, you must get asked that constantly?
JKR: I do. I get frustrated with myself more than anyone else. You'd think by now I would have an intelligent and amusing answer to that question, but no I haven't found one yet because the truth is I do not know where it came from, I just don't.

He strolled into my head, fully formed, a scrawny little boy and I knew he was a wizard and I knew he didn't know he was a wizard and I kind of worked backwards and forwards from it. I felt this incredible upsurge of excitement at the idea of writing the story.

Now Harry's got so big do you think it's inevitable in the British way that there will be a backlash against him because we build things up and knock them down so next year we'll be saying - Oh it's not actually that good, we don't like him anymore?
JKR: That happens, that happens. I mean obviously I've only very recently really had any dealings with the press and television or anything like that and I've been watching that happen to people I admire for years.

You don't even have to be in the biz to have seen that happen. So to an extent I expected it - on the third book I expected that to happen and it didn't really happen then so I was due.

Is the character of Rita the depiction of your relations with the press?
JKR: Well I'll tell you the truth but I doubt very much that anyone's going to want to hear this. I tried to put Rita first in Philosopher's Stone. When Harry walked into The Leaky Cauldron for the first time and everyone said - Oh Mr Potter you're back - I wanted to put a journalist in there - she wasn't called Rita then though but she was a woman.

And then I thought, as I was sort of looking at the plot overall, and I thought that's not really where she sits best, she sits best in four when he's supposed to come to terms with his fame.

So I pulled Rita out of book one and planned her entrance for book four and I was really looking forward to Rita coming in book four.

The first time ever, as I sat down to write book four, my pen kind of metaphorically hesitated to go for Rita because I thought everyone will think that she's my response to what's happened to me.

Well people can believe it or not but the fact is that Rita was planned all along. And did I enjoy her a little more for what's happened to me? Probably I did - I probably did yes.

You put a little more venom in didn't you?
JKR: Venom - would you say so? No I wouldn't call it venom.

Now the future. Lupin's going to come back in book five isn't he?
JKR: You'll see Lupin again in five yeah, yeah - do you like Lupin?

Oh yes, he's my favourite.
JKR: Yeah and me. I always looked forward to writing book three because of Professor Lupin, I love him. You see a lot of old characters in book five. I'm not even going to try and tell you what happens in book five, I'm just recovering from the stress of book four.

You've left us on such a cliffhanger. And how are we with the film at the moment?
JKR: It's ongoing, still haven't got Harry which is a bit of a worry. But it's going really well, I've seen some things and they look incredible.

It's the most amazing experience to see - because I've been very lucky, I've been given a lot of input into how I imagined things and they're really trying to recreate what I see inside my head and it's the most extraordinary experience to be able to physically see Quidditch or Hagrid's hut - it's lovely to see what's been in your head for ages, it's wonderful.

Does it annoy you sometimes when the press and people just talk about children's books and they only talk about Harry Potter without realising there's a whole wealth of other children's books out there?
JKR: Yes it really does. Children's books have existed for quite a long time in press terms in a bit of ghetto when you look at the coverage that adult books get.

And then you hope that that might change and people say to me - Harry Potter, you know, we want to read it as well - it's a crossover book but loads and loads and loads of children's writers deserve to be and in fact are read by adults.

They might not be quite as famous for it than Harry is, but people like Jacqueline Wilson, David Almond, Aidan Chambers who has just won the Carnegie, Henrietta Branford I really admire but she died unfortunately two years ago, there's loads of people out there - Philip Pullman - wonderful writers.

A few short messages from kids before we finish. Harold Ryan who's 10 from Catford says: "What Hogwarts school house was Hagrid in?"
JKR: Err you have to guess because you might be finding out at some point.

"How do you feel about the Americans changing the title of your first book to Sorcerer's Stone?" from Rachel Gummer from Market Rasen.
JKR: They wanted to call it something different and I said well how about Sorcerer's Stone as a compromise. In retrospect I wish I hadn't changed but to be honest with you I was so grateful that anyone wanted to buy my book at all that I was maybe a bit too compliant about that.

JK interview Part 4 - questions and queries

There are lots of Latin names in the book and Roman names like Severus Snape - did you do Latin at school and enjoy it?
JKR: No I didn't do Latin at school, I did classics at university.

What was the original working title of Chamber of Secrets?
JKR: Harry Potter and the Half Blood Prince. I quite liked that title, unfortunately the story bore no relation whatsoever to the title by the time I'd finished.

And if you were offered a post as a teacher at Hogwarts what subject would you most like to teach?
JKR: Oh I think definitely Charms - I see that as the most imaginative bit of magic because you're adding properties to an object.

You wouldn't fancy Defence against the Dark Arts?
JKR: No I'm too much of a coward. I'd have to be really in a corner before I come out fighting but then I don't generally.

People say that Firenze was based on a friend of yours - the centaur - but we've hardly seen anything of Firenze.
JKR: Well just keep your eyes open.

Does that mean? The centaur's prophecy at the end of Philosopher's Stone ...
JKR: He'll come back. Well enough said, not everyone's read book four.

And Gilderoy Lockhart, one of my favourite characters...
JKR: Gilderoy's left in, he's still in Saint Mungo's Hospital for Magical Ailments and Injuries because his memory's just gone but I'm making no promises about Gilderoy.

Was he good fun to write because he's the opposite of everything he wants to be?
JKR: I loved writing Gilderoy but I've got Rita now, you see I love writing Rita in the same way that I loved writing Gilderoy.

What advice would you give to young writers? That's from Holly Hewitt.
JKR: I would say firstly and most importantly read as much as you possibly can, you don't have to read Harry Potter books, I'm not trying to flog it but only by reading will you get a really good idea of what, in your opinion, makes good writing.

You'll learn to recognise what doesn't work and you'll expand your vocabulary - always useful. After you've done that write about things you know - your own feelings and experiences - which is always a good starting point.

Resign yourself to the fact that you will not write something good first time, you're going to waste a lot of trees before you hit your stride and you will imitate people you admire first and that's fine - everyone has to start somewhere. And most importantly persevere - keep persevering.

If you had an invisibility cloak what would you use it for?
JKR: What would I use it for? I don't think I can say it - it's a secret.

Does the whole merchandising, that's about to kick in, worry you slightly - are we actually going to see Gilderoy Lockhart haircare products?
JKR: I think that would be quite funny actually. Does it worry me? Yes it does, in all honestly yes it does worry me. It's going to happen because that's what happens with films - there will be merchandising. I have seen early examples of the film stuff they're doing, I have no objection to it at all. But yes it does make me jumpy, yes it does.

I see those hormones kick in in this book, are we going to see Harry becoming even more like Kevin the teenager, are we going to see him going - Oh Sirius I hate you, I wish you were back in Azkaban?
JKR: I think Ron's more like that isn't he - Ron's more Kevinish. Harry's got so many worries, he needs his friends, he can't afford to alienate them. He's more your sensitive hero isn't he. Yeah more of that stuff happens.

Are there any special wizarding powers in your world that depend on the wizard using their eyes to do something?
JKR: Why do you want to know this?

Well because everyone always go on about how Harry's got Lily Potter's eyes.
JKR: Aren't you smart - there is something, maybe coming about that, I'm going to say no more - very clever.

The significance of the place where Harry and his parents lived - the first name...
JKR: Godric Gryffindor. Very good, you're a bit good you are aren't you. I'm impressed.

You're not going to tell me but ....
JKR: My editor didn't, I said to her - Haven't you noticed the connection between where Harry's parents lived and one of the Hogwarts houses? And she said no, no - I'm not being rude about Emma, she's a brilliant editor, the best ever. But no she didn't pick that up either, you're a bit good you are.

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