Katie Price's mobile phone bleeps, and she reads her message. "Maggie's just texted me," she says. "I've been shortlisted for the book awards for my Pony Club book." Nicola Partridge, one of her managers, lifts her head from the menu and nods. "You've been shortlisted? It's in your itinerary, good," she says.

Price, aka Jordan, has reinvented herself in recent years. The former topless model is now a bestselling author of memoirs, toddlers' books, children's novels, teenage novels - though, strictly speaking, she doesn't write the books herself. Her most recent novel, Crystal, has outsold the entire Booker shortlist. She also has her own lingerie range, perfume, calendars and will soon be launching Katie Price make-up and bed linen and the Katie Price credit card. And there is the successful reality television show with husband Peter Andre, now into its fourth series, in which they argue loudly, bring up their children publicly, and share their news, good and bad, with the rest of the world as it happens. Her singing career is still in its infancy - though it did not get off to quite the start she hoped for with a horrendously out-of-tune Song for Europe. She is thought to be worth upwards of £30m, and her plans, she says, are to conquer the world.

Price has not exactly banished Jordan. The two coexist happily in the one outlandish body, though it can cause confusion. The official Jordan website displays her classic old poses. She greets us hospitably: "Feel free to look around - make yourself at home! Wet dreams! Jordan." (Actually, looking around is anything but free: £3 a month, or £25 a year with extras.) Turn to the Katie Price website, and it's all fluffy pink, cutesy hearts and modest attire. "Feel free to look around. Make yourself at home! Katie X." Some people ask for interviews with Jordan, some with Katie. Her books are written as Katie Price, but she signs them Jordan. Ask her the difference between the two, and she'll say, "Nothing." Ask her management, and they don't know where to start.

Jordan is a very 21st-century phenomenon - the ultimate product of the "reality" era. She is a walking-talking, product-flaunting, money-milking paradox. She shows the public everything about her life, but is a control freak. She prides herself on keeping it real, but thinks of herself as the supreme construct. Her books sell by the million even though she doesn't write them. She's a one-time Page 3 girl who last year was named Cosmopolitan Woman of the Year, and Grattan Celebrity Mum of the Year.

We meet at an Italian restaurant in Brighton. She is accompanied by two managers, two of her three children (two-year-old Junior and eight-month-old Princess Tiaamii) and her brother Dan. It's hard not to address Price's chest - not because of what is on show, but because of what you expect to be. When Price started modelling, she was a 32B. But she always wanted bigger breasts, so she gradually enhanced them to a double G. Recently, she has had her breasts reducted. None of this, of course, is news to her fans. Those who follow her closely, or those who are acquainted with OK! magazine (where she writes an advice column), know all about the cosmetic surgery, the rubbish boyfriends, the feuds with Victoria Beckham, the abuse she once suffered as a child at the hands of a stranger, the occasional threesome, the abortion, the jungle, the televised courtship, the televised marriage, the miscarriage, the postnatal depression, her disabled son, Harvey, and Pete's "cockalicious" trouser snake.

Today she is Katie Price at her most demure - pink round-neck jumper, pink corduroys, pink boots, pink belt, pink bracelet, pink handbag and matching daughter dressed head to toe in pink. What strikes me more than anything is how small Price is - tiny frame, tiny pretty face, big voice. "You'll love this place," she says. "I've been coming since I was 15."

She's feeding Princess from a homemade jar of liquidised mush, as she talks. "Mashed potato, swede, broccoli, lamb, peas, you name it." Did she make it herself? "Yeah, I'm not good at everything, but I am good at a roast lamb - it's very fattening how I do it, though. Like my mashed potato - tons of butter. I make sure I take out Princess's food first, though, before I add all the butter and unhealthy stuff."

It smells all right, I say. "Course, it's all right. I'll be putting a cook book out next! My recipes." And I can see the figures ticking over in her head. Children's recipes? "Yes, absolutely." I feel as if I should be on a percentage.

It's early March, and Price, 29, is on the cover of today's Sun in a "saucy air stewardess's uniform" with an exclusive - she's going to buy her own plane, paint it pink and call it Booby. Is that true? "Yes, I am looking. I don't think it will be called Booby, though, and it's not going to be all pink, either." It's another business proposition. She plans to recoup some of the cost by hiring it out.

Lunch with Price is a reversal of conventional social etiquette. Whereas normally you'd be embarrassed to talk about anything too personal, here it seems rude not to. "In real life," she says matter-of-factly, "my boobs never look quite so big. They always look bigger in pictures... Come on. Eat up!" She segues happily between Princess's lunch and her anatomy. "I'm not particularly happy. I've had two reports done by surgeons over here and they say I need them redoing. They look all right in clothes, but they're not right... But it's fine, it's a problem that can be sorted." Why did she want to get so big in the first place? "I always wanted big boobs." I ask if it was a marketing stunt - a way of keeping in the public eye. She shakes her head. "I didn't do it for my work, I did it all for me... Whatever people say, I haven't got body dysmorphia. Not at all."

At the same time that she had her breasts reduced, she had a nose job, with which she's pleased. What was wrong with her nose? "It was fine before, but the doctor was a perfectionist and I said if you could change anything about me, what would it be, and he said my nose, so I just did it. You can buy designer outfits, I just bought a designer nose. It's not everybody's cup of tea having surgery, but I'm not planning to have any more."

"Enjoying your lunch?" Dan asks.

"Botox is fine," Price says, ignoring him.

As we chat, Dan keeps Junior happy by telling him stories about a monster that lives in the cupboard behind us. He's four years older than Katie - a quiet, handsome man. Dan studied international business management at university, and now divides his days between working for their stepfather's fencing business and managing the Jordan and Katie websites. "It's a waste that he went to uni," says Price. Dan doesn't seem to think so. Is this a domestic? "No, we don't domest," she says.

Price grew up in Brighton. When she was four, her parents split up. Price is her stepfather Paul's name. She says she's lucky having two dads she gets on with. Her younger sister, Sophie, is 18 and just starting out on a modelling career. Price's parents were loving but strict. They did not allow her to go to youth clubs or even have a paper round lest she fall under the wrong influences. "Paul didn't like me wearing make-up or earrings. They were quite protective. If there was a boy I fancied, I used to write a note and give it to Daniel to give to a boy. Do you remember?" She looks at Dan, who's still telling Junior about the monsters.

"She was just into her girlie stuff, anyway," he says. She had to watch him play football on Saturdays, he had to watch her doing gymkhana on Sundays. Sunday evening they'd argue about watching Black Beauty or the motor racing on the telly.

"I was just into horses. Country girl - like I still am. I've got six, and Princess's is in the field, waiting."

What was she like at school? "I hated it. I was only happy when I was with horses. My mum couldn't afford for me to go to the Pony Club - that's why I like doing the Pony Club novels. I had the ugliest, hairiest pony in the yard, and you'd get girls with really nice ponies and their mum and dad involved. They were all posh girls. I just come from a normal family, working class. I didn't own a horse, I had it on loan. He was 18 years old, 14 hands, bay and he was called Star. Brown-bodied, black mane." She left school at 16, worked in a care home and started to train as a nurse.

One of the things Price is most proud of is that she has not changed over the years. Another is that she doesn't give a toss what anybody thinks. Yet at the same time so much of what she says and does is calculated for effect. A few weeks ago, the News Of The World ran a domestic "exposé" from a former nanny. Price is now suing the newspaper. "If I'd wanted to, I could have let the paps take all the photos they'd wanted to show we're this happy family, but I don't need to do that, I don't need to prove it to anybody. So even if they follow me, I try my hardest to lose them, because why should I let them get that picture?"

Fair enough, but here she is today for an interview, children in tow, being a model mum. She also eats for England and makes sure I notice, casually referring to rumours that she has been starving herself into her size sixes. "I've got funghi e prosciutto. It's supposed to just be mushrooms and pasta and cream sauce - Junior, don't shout - but I've got extra peas and onions. And I had avocado, mozzarella and tomatoes and finished all that. But I forgot I'm on a strict liquidised diet. And I will be having a pudding as well."

I raise my glass of wine and toast everybody's health. Price says she doesn't understand how people can drink at lunch, and she's certainly not going to be toasting good health, anyway. "It doesn't matter if you cheer on good health - it didn't happen in my case, did it? So that's a load of crap, isn't it? It didn't bring Harvey good health, or me." Is she ill? "Well, I got cancer when I had Harvey, that's about it." She shows me a scar on her finger. "I nearly had to lose my finger, it's called leiomyosarcoma. I'm not toasting nothing. I'm not jinxing myself. Hahaha!"

Harvey is now five. His father is the footballer Dwight Yorke, who insisted on a paternity test because he didn't think the baby was black enough to be his. The couple had split up by the time Harvey was born. Harvey's life has been just as fully documented in OK! as Price's has - he is autistic, partially blind, weighs eight stone, has learned to say, "Fuck off", and Price loves him to bits. How is he? "He's good, but not his behaviour. You know what they reckon he's got now? It's called Prader-Willi. An eating syndrome. He never knows when he's full."

Claire Powell and Nicola Partridge, her managers, can never relax when they are out with Price - they are always on pap alert. They shunt their eyes from one corner of the restaurant to another. Finally, Partridge says she thinks she's spotted one. She points to a man standing outside with a suspicious-looking bunch of bananas.

"I think they're camping outside right now," Powell says wearily. It must be such a strange life - half the time courting the paparazzi, the other half shooing them away. Nobody approaches us over lunch. "Can I ask you a question?" she says. "What's the difference between being a celebrity and being famous? See, I think being famous is when you're known worldwide, and being a celebrity is when you've just been in Big Brother and had your five minutes of fame." So is she famous or a celebrity?

"Neither. I'm in an odd category. Because I'm more than just coming out of Big Brother, but I'm not famous worldwide. I am in a few countries. So I'm not sure what category I'm in. I'm the girl who's done well out of herself."

Fame is a pet subject. She says she always knew she wouldn't be pinned down to an office job. "I wanted to be a pop star or jockey or model. It's really strange. I asked Pete the same thing, and he said the same - he knew he wouldn't end up doing a normal job."

Who are her role models, her heroes?

"I haven't got any. I don't care who's famous, I don't care what anyone does. I've got no role models. I couldn't give a shit about anyone else." There's no one she admires? "There's no one I want to be like. I couldn't care who walked in the room." She pauses. "I'll tell you who I want to meet, the original Black Beauty, the horse - I'm obsessed with black horses."

At 17, she became a glamour model. Jordan was created on the spur of the moment. A Page 3 girl dropped out, she turned up, the paper wanted a name to apply to the caption, she and her agent dreamed up Jordan, and that was it. From then on, she was never out of the tabs and mags. Whenever she went out clubbing, which was often, she'd be papped. Then the pictures would be recycled until her life was reduced to endless nights of drunken stumblings. Reading her three autobiographies, so much of it sounds miserable - she drank because she was insecure, she made an idiot of herself because she drank, she had rubbish boyfriends who made her feel more rubbish about herself, and on it went. She insists that however miserable she has been in the past, she wouldn't change a thing today - her experiences have made her the woman she is. "I don't regret anything, apart from Eurovision. That is it. That's the worst thing I've ever done in my life." It was 2005 when she sang Not Just Anybody in a pink, skintight catsuit while heavily pregnant.

Did she embarrass her family with her career choice and indiscretions? "All the time. Everyone feels embarrassed. They don't know what's going to come out of my mouth next." Although her parents were strict, they were not really in a position to disapprove of her career choice. Her grandmother had worked as a topless mermaid. "And if it was good enough for my nan, it was good enough for me."

"I was dead set against Kate doing topless modelling from day one," Dan says. "I was like, why you? I can't buy that paper no more. It was a bit weird. I play football on Saturday and in the changing rooms, all the banter..." How did he cope when his mates made laddish remarks about his sister's body? "My normal response is, 'Yeah, they're not bad, and they feel all right, too.' Then they're like, 'What!' And that's the end of the conversation."

Life divides neatly in two for Price - pre-jungle and post-jungle. In 2004, she went on the reality show I'm A Celebrity... Get Me Out Of Here! as Jordan and came out as Katie. While many celebrities lose their dignity in the jungle, she found hers. She came across as vulnerable, funny, needy and very human. She fell in love with the Australian singer Peter Andre. He was a pop star in terminal decline, she was a Page 3 girl approaching the end of her shelf life. Both were in need of reinvention. While she was in the jungle, her mother approached Andre's management team and asked if they would take on Price. They agreed, so long as they could remould her. "I believed what I had read in the papers, and when I met her she was totally different," Powell says. "I thought if she continued doing glam, by the time she was 30 there'd be lots of other people around, and that she could do a lot more than she was doing. I think Katie thought I was trying to kill off Jordan at the beginning. She thought, my God, this girl is trying to ruin everything I have built up over all this time, so that's why we clashed a bit."

Was she trying to kill her? "No, I wasn't trying to kill off Jordan because she's made an awful lot of money and Katie is Jordan. All I was trying to show her was, once you have a team around you that you can trust and only want to take their percentage to make you different and bigger, how much bigger and better you will be, and how much money you will earn." Powell believed that, with the right image, Price could sell anything. "For the first six months it was difficult, because I'd say don't put so much make-up on. When we first started managing Kate, she'd have three sets of eyelashes on and two lots of fake tan. She would go and do a red carpet, and she'd want to have a drink so she'd have that confidence. She would then want to be made up because she could hide behind it, and it would give her more confidence."

Price was a strange mix of self-belief and uncertainty, Powell says. "She was very confident in front of the camera - she could stand there and pose in front of a thousand people and not be nervous. But if she was going down a red carpet fully clothed, she'd feel very nervous."

"I think that's a nice thing," Price says. "If people are really confident, it's unattractive."

Out went Jordan, in came Katie, the homely girl's girl. Instead of dodgy footballers, drunken escapades and explicit revelations, there was Andre, marriage and endorsements galore. The fact is, she says, even though she gave the impression she was promiscuous, she never was. She didn't sleep with many men, it's just that she told us all there was to tell about the few she did sleep with.

When I ask about her boyfriends, she says she won't go into details. "I'm not disrespecting Pete. If people want to know about that, they can read my book." Classic Price.

When she says "book", she means books. She asked for a £1m advance for her first memoir, Being Jordan, and was turned down. She ended up signing a deal with small independent publisher John Blake for £10,000. Being Jordan sold more than one million copies. The latest memoir, the third, Jordan: Pushed To The Limit, was as we went to press number three in the hardback charts. If you look for a ghostwriting credit on the cover or inside jacket of her novels, you won't find it. Only when you get to the fine print is there an acknowledgement that copyright is jointly owned by Katie Price and Rebecca Farnworth. She says she is closely involved in her novels. "I talk in a tape and say the stories that I want. Rebecca then writes each chapter. It comes back, and I read it through."

Powell clarifies. "Then Kate re-sits down with it and says, I want it to be this or that, or more powerful, and they just write it into book words."

Why does she think her products are more popular than, say, Victoria Beckham's? "Probably because I work and do the promotion. I'm not up my arse and I've not got the attitude to say anything I do is going to go to number one. It does go to number one, but I do put my time, effort and promotion into it."

A couple of days later we meet at the lingerie shoot for her Katie Price underwear. In an echo of the Dove campaign, she has invited larger female fans from her website to join her in the photo shoot for the range that starts at DD. She is wearing loose tracksuit bottoms, pink and purple curlers in her £2,000 hair extensions, and looks like something straight out of a Victoria Wood sketch. Dan is here snapping away for the website, while little sister Sophie offers her support.

Price's feet are an unlikely shade of brown. Is that colour real, I ask. She laughs. "What is my persona? Real or fake? There's your answer. If you got something like that from the sun, you'd be in trouble."

I talk to one of the women who have been chosen to model alongside her - it turns out Angie is a cousin of a cousin of Andre's and doubles up as Price's beautician. As we chat, I notice Partridge standing by my side. She is whispering urgently. "Simon, I'm sorry, Katie would prefer you not to talk to the girls." Price thinks the girls are nervous.

A few minutes later, a woman from George at Asda, which sells the underwear, introduces herself. I start to talk to her about why Price and George at Asda suit each other. From the other side of the room, somewhere underneath a hairdryer, Price is shouting at me. "Simon, her name's not Katie Price. This is supposed to be about me."

I walk over to her, assuming she is joking. But she isn't.

"Are you objecting to the fact that I'm talking to them or that it's about you?"

"Because the deal is about me, not other people, and it's not fair to put them in that position. Unless you cover it with my management. Your job is to interview me, not other people. That is the job description. Am I right or wrong?"

I tell her that she's right in a way and wrong in a way, but it's good to see her bossy side.

"I don't think it's bossy. It's called sticking to what you're supposed to be doing. There's a difference. What star sign are you?"

"Capricorn."

"Ah, no wonder. My Dad's a Capricorn, and my brother. I bet you're really stubborn, aren't you? I'm a Gemini, there are two of me, so I can be nice, but I can be naughty in a minute."

"Do you have a stubborn streak?"

"I wouldn't say stubborn. I just know what I want, and if I want it, I'll make sure I get it."

Next time I see her she has transformed herself into Jessica Rabbit - charcoal-grey bra and knickers, diamond stilettos, shocking pink nails, dazzling green-hazel eyes. The shoot is well- intentioned, but seems almost cruel - a couple of the less photogenic women are nervous and freeze in the glare of the flashlights.

Powell is talking about Sophie Price's burgeoning career and explaining why she won't be doing topless. "Page 3 has changed an awful lot over the past eight to 10 years. There's nothing wrong with topless, and I'm all for women who are liberated. But you can do glamour and be sexy without actually showing your boobs. Once you've gone topless, everyone sees you as a topless model."

Which is what makes the transformation of Katie Price all the more amazing. The most fascinating thing about her metamorphosis is that women and girls now form the bulk of her fan base. Price knows that in the past she has been anything but popular with women. "When you're a Page 3 girl getting your tits out, you're just aimed at men so women do find you a threat." Nowadays, she thinks women find it easy to relate to her - the kids, Harvey's disability, the hard-luck stories with previous men, the honesty.

Dan tells me that the Katie Price website is now more popular than the Jordan website. Does he ever get confused between the two? "No. The difference between the two sites is the Jordan has a forum and 24-hour chat room. We have to monitor it. The Katie Price site doesn't have a forum or chat room, so it's safe for children to go to - no predators out there." Will Jordan become history at some point? "Well, I don't think so - Katie signs everything Jordan." Why? "She won't let it go because it got her where she is."

When Powell first met Price, she asked what her ambitions were. Price said she wanted to sing. "I said men will not go out and buy albums. If you want to have a music career, you've got to latch on to women." Over time, "Katie Price" has been nurtured. "The message now is that it's OK to like Katie, it's OK for your daughter to be like Katie. She was doing sexy today, but OK sexy, nothing harmful, threatening," Powell says.

In many ways, the reality show leaves her more exposed than Jordan's undressing ever did. When she visits the doctor for a pregnancy check-up, we find out at the same time as her that the baby is dead inside her. When Andre loses his rag and says she's the moodiest, most difficult woman in the world, we hear his rant uncensored. Did she not think of turning off the cameras when she heard about her miscarriage? She shakes her head. "Nicola was filming it, and she said, 'Do I turn it off?' I said just keep it rolling. It's real." Could she imagine her and Andre splitting up on TV? "Well we're not going to split up." But the implication is that if they did, of course the cameras would be there. Their relationship began in front of the cameras and has evolved in front of the cameras. I wonder if they ever feel they are in The Truman Show; that they wouldn't exist if the cameras were not there? "Not at all." She gives me a look, as if to say that's bonkers.

What if the kids didn't want to be on the show? "They wouldn't be on it." Would she keep doing it? "That's me, yeah. But I don't know why they wouldn't want to be on it. The way I look at it is, you know when people buy a video camera, go on holiday, they're filming themselves, and they've got the memory there for ever. How much better is it having a camera following you around, getting everything? You couldn't even buy that. It's brilliant. We've got all them tapes from the moment they're born. I wish I had tapes of me growing up from the day I was born. I think it's brilliant".

She has a knack of working herself into a lather out of nothing. At times, random thoughts seem to hit her and she flies into a fury. "I can't stand people, celebrities or pop bands posing with disabled kids to try to get a hit record," she says apropos of nothing. "That really fucking pisses me off. Try and have a kid yourself with disabilities, then you wouldn't be posing around with kids."

But you often pose with Harvey? "He's my son, and I may pose with him, but I also talk about what it's like to be a mum with a disabled child, and believe it or not I get so many emails from people who say it helps them and they ask how they get equipment, things like that. I'm in control when I do it with Harvey."

Control is such an important word for her. Price is very controlling about her image. The one area over which she doesn't have control is the reality show. Powell (who appears regularly in the programme) and her partner own the production company and do not allow Price and Andre to see the show before it goes out. I ask Powell if Price and Andre are ever shocked by what they see? "Yeah, sometimes, they're like, 'Jesus, we really went for it then.' But it's a reality show, and if it was a fluff piece it wouldn't still be on TV." In the last series, we saw Price trying to crack America - Powell apologises for waking her early in the morning, but says that eventually she will thank her because it will make her globally famous. Price replies that she doesn't want to be famous, she wants to be a billionaire.

Tell me about money, I say. "I don't ever discuss money. It's a really unattractive thing to do." But you did say you wanted to be a billionaire? "Well, you've got to have ambitions, haven't you? I don't think even Paul McCartney has got a billion, so there you go."

It's incredible what she's made of herself and for herself. Whereas fellow OK! cover girls Kerry Katona and Jodie Marsh come across as victims, Price seems to transcend her misfortunes. When Dwight Yorke leaves her with a disabled baby, she appears strong; when she gets cancer, she fights it; when she miscarries, she turns it into poignant television. Does she consider herself lucky or unlucky? "Both. I'm both. Yeah, both. Personal life, always shit happens. Career-wise, always an up. I love it."

Price is living proof of how you can conquer the world with a pretty face, a decent surgeon, determination, tough management and chutzpah. I had assumed she simply aspires to fame, but that is wrong. She aspires to success - any success - and that success is best measured in money. No wonder she has become a role model. Price is a figure of hope for many people - if Katie can do it, without any great talent, so can we.

There are so many things left to endorse, she says, so many ways of making money - not least from her newly removed implants. She recently announced she was going to put them on eBay for £1m. "They're in my safe at home at the moment." And she really thinks she'll get £1m for them? "Yes, I do. Yes. I might actually put them on for a bit more, because I want £1m in my bank account, and I want to give some money to charity. I'll be greedy this time."

· The new series of Katie And Peter: The Next Chapter starts on March 27 at 9pm on ITV2.