Fame, fashion and victory over the paparazzi

Lily Allen is unpacking. At least, I'm told it's Lily Allen. The bustling little figure in a baggy Aberdeen football shirt and jeans looks more like a 14-year-old boy than a 23-year-old pop star, and the kind of 14-year-old boy who is still fond of his Lego at that.

The 14-year-old boy keeps apologising very sweetly, very politely. He says he is sorry, and do I mind, he hopes I don't, but he must, must, get all this sorted out. Once his room is all tidy, he'll be able to relax. So he can't be a 14-year-old boy at all. But whoever he is, he does not seem at all like a drunk, druggy, foul-mouthed tabloid wild-child who's too smart and acid-tongued for her own good, and a bit of an icon really, for all that is just too terrible about Young People Today.

Allen has just flown up from London to Glasgow, heaving a couple of overstuffed suitcases with her. In a couple of hours she will officially start her world tour, playing a 2,000 capacity venue (sold out), then getting on the tour bus and heading straight off for the next night's performance in Manchester. She recently released her second album, It's Not Me, It's You, and its arrival has not been "difficult", in the way that second albums traditionally are expected to be. Instead it is a critical and popular hit, just like her first album, Alright, Still.

If anything, Alright, Still was more "difficult" since its all-conquering arrival in summer 2006 was accompanied by an avalanche of scurrilous publicity, about Allen's troubled schooldays, her involvement with drugs, and her alleged promiscuity. She was slated for being a fraud, a Mockney, passing herself off as streetwise, when she had only made it, and so young, because of her well-connected father, the actor Keith Allen, and her well-connected mother, the film producer Alison Owen. Britain, fake meritocracy that it is, prefers to believe that merit can be effortlessly faked.

Considering that she is now an established star, Allen seems rather more excited than she should be that a couple of travelling wardrobes have been deposited in her shabby dressing room, and also rather more excited than she should be that she has her own dressing room at all. She pulls clothes out of her cases, and hangs them up methodically. Her tour manager, Vicky, walks in.

"Lil, you should see your new bedroom."

"I've seen it. Isn't it great?"

Vicky picks up a little green-and-gold biker jacket.

"That needs a hanger," says Lily. "And what about these? I just spent £500 on dry-cleaning this morning ..." She heaves out a big pile of clothes, all sheathed in plastic, and starts liberating them.

"What about this for tonight? Isn't this cool? Giles Deacon made me a whole load of stuff. It's nice isn't it?"

She throws off her clothes, shrugs on a little black dress and poses in front of the mirror.

"That's quite cute. With heels. Zip me up."

She hoists herself into a pair of giant gold heels, and Murray, her PR, zips her up, as requested.

"Do I look huge? Does it make my legs look huge?

"What, long?" says Murray.

"Yeah. Does it make my legs look long? Because if it does, then I won't wear it."

Murray looks cross that she's being ridiculous enough to ask about fat legs. "Can you move in those heels?" he asks.

"Course I can. Look." She pirouettes theatrically. "I can do anything in a heel. I did that whole Koko gig in these. But do I look fat? Maybe tights. Shall I wear tights?"

"Fancy tights?"

"I've only got thick black tights."

We all agree that thick black tights are very, very wrong, and the costume for tonight has been decided on.

"Look. There are more T-shirts. I need to keep the comfy T-shirts on the bus, to sleep in. Maybe Grace Jones can be a pyjama."

It is agreed that Grace Jones will be thrilled.

"Will you put my ... er ... sedatives on the bus," Lily asks Vicky. I look at the zip-up bag of prescription pills in Vicky's hand and feel a pang of concern for this funny wee controversy machine. "Sure," says Vicky. "And your dressing gown."

Allen takes off the Giles Deacon dress, hangs it up, puts on a white vest and jogging pants, and thwumps down on the sofa. "I'm so happy I can tour like this now," she says. "Before we had to move everything, literally, off the bus every day. Everything would get lost. Tomorrow, in Manchester, I can walk off the bus in my Uggs, come into the venue, and have breakfast. When I go into the dressing room – My Own Dressing Room – all my stuff will be here in the wardrobes, so I can have a shower, and get set. You don't know how much of a fuss I had to kick up about this."

Everybody else has left the room, at Lily's request, which is surprising. People who are not always treated well by the press are generally nervous of journalists, and prefer to keep a minder on hand during interviews. Allen, quite certainly, is not always treated well. When the release of her first single, "Smile", catapulted her into a long, hot summer of massive exposure, an advertisement was even placed in the local paper in Islington, where she had lived as a schoolgirl, offering cash for racy information. That level of attention has never really abated, and was most intrusive at the time when she became pregnant by her then boyfriend Ed Simmons of the Chemical Brothers.

"It was a really weird, horrid time. What was worst about it was that I didn't engage with what was really happening, on an emotional level, because I was dealing with the press side of it. I couldn't really comprehend what was happening, because I was concentrating on trying to control the story." She splays her hand out, admiring the green varnish she's been putting on her short, neat nails.

"People shouldn't have known that I was pregnant anyway. When it became obvious that they knew, we had to say to them: 'I'm not three months yet, please don't write the story, because it's too early and we don't know if it will go wrong.' Of course, they ran it, and it did go wrong, and that was really ... just ... not a nice time."

After she lost the baby, Allen booked into a residential therapy centre, and broke up with her boyfriend. She didn't really have the option of trying to deal with her turmoil quietly, with her family, at home. Home, for years now, has been besieged by photographers. Allen sells newspapers, and everybody wants a piece of her.

She's very happy today though, because she thinks all that might be over. The day before we met, she'd gone to the High Court, and obtained an injunction protecting her from paparazzi harassment. "I know already," she says with some optimism, "that it's going to change my life."

The pictures that made her snap have already appeared in the press, and showed an angry Allen launching an aggressive attack because she'd got herself involved in a car crash. The reality was different.

"Seven cars had been chasing me since I left home. I turned into a T-junction and they all ran a red light, then tried to overtake on the inside. A woman had to slam the brakes on her car as they cut in. She had two children in the car, a baby in the back seat, a six-year-old in the front. I braked too, of course, and this guy ran into the back of me. I got out of the car. I was shaken up. There was a lot of force. I was really angry. I went up to him and said, you know, 'What the fuck are you doing? You can't do this.'

"Instead of talking to me, like a decent human being would at a decent human level, he got his camera out and started taking pictures, and I just thought, 'I've had it with the press, I can't do this any more.' It was mental. And I got back into the car and called my lawyer.

"He called up a judge and booked me into court the next day. And luckily the court understood where I was coming from and granted an order to stop the harassment. They are now not allowed to wait outside my house, follow me in cars, wait for me outside friends' houses, or my family's houses. Take pictures of me with my friends and family. They can take a picture of me when I'm walking out of a restaurant or out of a shop and that's it. If they follow me I can serve them with a court order. I'm beyond happy.

"It's like I've been allowed to have success and a life. Because sometimes it makes you feel like a caged animal, being followed by 20 men with cameras all day. The second I walk out the door, it's like that. It cost me a fuck of a lot of money but it's the best money I've ever spent. I'm very pleased and very grateful."

Certainly, Allen had a lot to deal with, very young, very suddenly. For her, though, because she'd already been building a fan base herself for some time, on the social- networking site MySpace, it didn't seem quite so instant.

"It was weird actually, I suppose. But for me it was gradual because one day I had 100 friends on MySpace, then it was 200, and suddenly I had 1,000. It was exciting, but I still didn't know what I was in for. I thought I'd already ... arrived. Then it just kept getting bigger.

"My mum says there was this really poignant bit for her, when I still lived with her and she came upstairs and ... I didn't have a really tough time when I was growing up, I'm not trying to say that, but I didn't have any friends at school, didn't really have any people in my peer group that I felt close to ... She came upstairs and I was on my laptop, and she said, 'Night darling, I'm going to bed...'

"And I said, 'Mum'.

"She went, 'What?'

"I've got the most friends in the whole of Great Britain.

"But I controlled it, and I still do control all of that. I don't think it will get so big that I can't control it, and I don't really want things to get to that stage. I feel like I've achieved far more than I could have hoped to achieve in this industry already. The bit I really hate – the paparazzi attention – is the only bit where I am out of control, and maybe I despise that bit because I'm such a control freak."

Allen thinks a lot about why she in particular should inspire such a frenzy of interest from the press. "People say that the tabloids and stuff have such interest in me because in the lyrics I let so much of myself out there already, because of what I sing, but I don't really see that. I try to find things to write about and be as honest as I can. I don't want to do generic love songs. Everyone does that."

Still, she does expose herself in her songs, and on occasion she has inadvertently exposed others as well. Her brother, now a successful actor, was very upset when she included on her first album a song berating him for being a waster and smoking too much dope.

"Alfie was hurt, and I think I learned a lot from that. I do have songs about my family on this album, about my mum my dad and my sister, and they're forgiving songs, nice and positive. The songs about men? No one knows who those songs are about, not even the people they're about."

However, if there's a significant difference between the nature of the lyrics on Alright, Still and It's Not Me, It's You, then the difference is that the second batch, on the whole, is even more intimate, mostly dealing with personal and private situations, drawing a lot on her relationships with her family, and on what come across as claustrophobic, walled-up affairs. There were stories like that on Alright, Still, but there was also a lot of commentary on Allen's adventures out in the world, with London portrayed as a bewitching, dark metropolis to which she had full access.

She herself is much happier with the new material. "I felt slightly fraudulent doing the last album, because people just gave me musical tracks and I wrote over them, like a cut-and-paste job. This time, me and Greg [Kurstin, her producer on It's Not Me, It's You] sat round and did it in a much more organic way, sitting at the piano, singing and writing songs together." It does nag at Allen, though, that she may at some point have "nothing more to write about".

She finds it "impossible" to establish a routine when she gets home from tour, and tends to take on more work just to give her a structure and the protection of a team around her. "When I really have to rest ... That's usually when I get into an intense relationship, put everything into a man."

And all you have to show for that are some killer lyrics?

"I sound a right nutter, if you put it like that."

Asked whose musical career she really admires, Allen says Kate Bush, "because she just manages to do what she wants. She's amazing. She does her creative work and keeps her privacy, and that's one of my ambitions."

And, in fact, it is very instructive to compare Allen and Bush. Bush too arrived very suddenly and decisively, with a single released when she was 19, "Wuthering Heights". Bush had previously been told to come back in a couple of years by EMI – Allen's record company – because executives were worried that her youth made her vulnerable. When her first album, The Kick Inside, came out, some of the lyrics were intimate, telling stories based on biographical material. People were scandalised in the late 1970s that a girl so young appeared to be writing about her sexual relationships. Even though the behaviour of the press back then was by today's standards highly respectful, Bush came to hate the interest in her private life, and now lives reclusively, withdrawn from the world. I can't imagine Allen, who seems curious and sociable by nature, ever being able to live that way.

Anyway, Bush is wealthy, having generated a huge income from the sale of her records. But the music industry has changed completely since Bush started making music, and Allen is no exception to the norm nowadays in that she doesn't get an income from her record sales. The money she makes is from touring – and living in a secluded mansion, bristling with security, refusing to appear in public, is an option unlikely ever to be in Allen's grasp. Even Michael Jackson can't do that any more.

"You can't make that kind of money now, it's over," she says. "Yet everything's so expensive now. House prices. I remember at the age of 14 looking in the windows of estate agents in Islington and seeing two-bed flats at £600,000. I'd think: 'How the fuck am I ever going to do that? Like how?' Maybe it was because my mum was a single parent, always re-mortgaging the house, that I became so preoccupied with money. But generally, the climate is so much more difficult for young people. I wanted to grow up really fast, so that I could start trying to earn some cash."

She looks approvingly round the dressing room that she's been in for a couple of hours, and will be in for just a couple of hours more. "I feel like this is home. It's really weird. Being on tour is sometimes difficult, being away from home and all that, but there is something quite comforting about it as well. Just getting on the bus, watching DVDs, like, being around 20 friends all the time."

Murray the PR bursts back into the room, sees Allen still sitting about in her casual gear. He tells her it's nearly eight o'clock and she really has to start getting ready. She doesn't seem nervous at all about the fact that she's on stage in an hour, and she says she's just edgy enough. She'll have one glass of wine before she goes on, to chill her a little, and take one on stage with her. She admits that she used to drink too much before she performed, and that it was no good.

"This is the first tour that I've felt really excited about. I love performing live, that minute before you come on stage, where you're a bit nervous and you walk out and everyone is screaming. And you think: 'I can't believe it.' Then you have to try to keep that reception. There's nothing better when you all walk off-stage, the five of you, turning round and saying: 'That was fucking great, wasn't it?' "

In an hour, when I see her again, Allen has walked out on-stage, and everyone has started screaming. She doesn't look like she's thinking: "I can't believe it". She looks poised, beautiful, sophisticated, relaxed. The 14-year-old boy has been obliterated. Allen's connection with the audience is immediate. She puts on an intimate, effortless, unfaltering show for them, and they love her – singing, dancing, applauding, cheering. The atmosphere is fantastically good-natured, and benign.

When she starts singing "Fuck You", her anti-racist, anti-homophobic song about the BNP and the Bush era, everybody knows the words and adopts her gestures, in unison. It's moving, seeing these young men and women, from this tough town, so open-hearted and celebratory, so in thrall to this girl, so engaged by what she has to say. The guys even sing along, like they mean it with all their hearts, to those lyrics that are so scathing about men. All Allen wants is to enjoy her success – success that is enjoyed by so many others as well – and also to have a life. That doesn't seem unreasonable. On the contrary, it seems like the least she deserves in return for all that she gives of herself.

'It's Not Me, It's You' is out now