Amid the chaotic whirl of Lily Allen’s new north London flat, the postman always rings at least twice a minute. There is a constant interruption of deliveries, principally Chanel dresses, handbags and other goodies. She takes the latest batch, walks past her grandfather Eddie, who has been living here for a while, and goes to her bedroom. I duly follow.
It is an arty mix of masculine dark walls, white-painted floorboards, original prints (nothing from her most recent fling, art gallery owner Jay Jopling, though), a mirrored chest of drawers surmounted with a framed painting of the Sex Pistols God Save The Queen record cover and a huge cushion-piled bed; and, oddly, slap bang in the middle of it all, a substantial roll-topped Victorian bath.

It’s anarchy, but it’s only skin-deep. She pulls open the top clothes drawer and reveals dozens of jewel-coloured Agent Provocateur silk and satin pants, neatly folded into separate plastic pocket holders; Stepford-Wife perfection. In her walk-in wardrobe, every pair of shoes is boxed and has a Polaroid of the contents stuck on the outside. In her kitchen cupboards and in the spice rack, all the labels face the front. And there is one overriding house rule: no drugs. ‘I don’t want people crashed out here all hours of the morning. I don’t want any drugs in this flat.

‘This is what I’m really all about,’ she adds, pointing to the ordered garments, shrugging off her vintage dressing gown (and yes, she has lost a hell of a lot of weight) and wriggling bra-less into a tight, black Phillip Lim couture dress.

‘It’s control. I have to be in control.’ Then she grins. ‘Even when I’m out of control I’m still sort of in control.
I know the point I’m going off the rails. But it’s my decision to go off them.’

Originally hailed as the quirky, kooky bright young thing of British pop when she launched herself through MySpace two years ago, Lily – daughter of hell-raising actor Keith Allen – rapidly became less known for hits such as Smile and better known for behaving badly, getting drunk, doing drugs, falling out of parties, crashing her own chat show and slagging off other pop stars. She also, famously, alternately berated herself or defended herself on her own blog.

She nods sincerely. ‘I’m not going to be doing so much of that (blog) stuff now. Thing is, for me, when stuff happens, I have to write it down. That’s what I was doing. Putting every emotion I was having out there on my blog. But it was too much. You can’t do it. It all gets twisted up. I’ve learned my lesson.’

She fuelled her own baptism of fire with her bloggings about being a mess and her bad behaviour. The newspapers were full of pictures of Lily stripping off in Cannes, falling flat on her face outside London’s Groucho Club and stories of a heated row with Elton John at the GQ Awards, where he allegedly bawled her out for being off her head (‘Not true, he’s a mate’), weeping after not winning a Brit (‘I wasn’t’), dying her hair pink, splitting up from her boyfriend, Ed Simons from The Chemical Brothers, after a horribly public miscarriage and then damning herself as ‘fat, ugly and sh**ter than Winehouse’, causing everyone to fear for her state of mind.

‘If you’d come to my place six months ago or two years ago, I wouldn’t probably be up by now,’ she says. (It is about 11am.) ‘There would have been empty vodka bottles everywhere, drugs, whatever. If you think, when all this happened I was 21. Becoming famous is all a bit scary and weird and I had no idea how to handle it.

‘On the one hand, it’s great – you get all this free stuff and party invites... and then on the other, I couldn’t even stay at my nan’s funeral to pay my respects because there were photographers all over the place. And God, I loved my nan.

'So much is written about you, and you look at it all with these photographs, and you think: “Everyone must think I’m a total t**t.” I don’t ever think I’m any different to anyone else. But suddenly I’m this cartoon of a party girl. If I didn’t know me I’d think I was a t**t, too.

‘So you go out and you get off your head. You get invited to parties and there’s free drink and drugs. Well you do, don’t you? What other 21-year-old wouldn’t do that?

‘Then you wake up and people are calling you ugly and fat and saying what a state you are. You have to deal with that or you can deal with it by just trying not to deal with it.

'And then something much bigger than all of it happens. At some stage the axe is going to fall. When I had my miscarriage I didn’t even know what I was going through, and I’m there and I have to put out a press release to say I was losing my baby. I didn’t deal with any of that at all. I just went out.’

She pauses and looks away. ‘The thing is, I didn’t actually start dealing with it until the baby’s due date. Then
it all hits you and you can’t escape and you have to just do something. You have to start dealing with reality.’

But Lily knows how to pull it back. She can turn the mad behaviour, the partying, the outrageous image on and off like a switch. Inside she is a carefully controlled, highly ambitious woman. The girl who just knew at a young age she was going to make it in the music business; the girl who is a perfect cross between her hard-working, highly organised mother and her wild, unpredictable father.

She looks up. ‘I had a dream last night my dad had died. That’s horrible isn’t it?’

There is a pause and I tell her that you always dream the opposite of what happens.

Instantly she laughs: ‘Oh God. That means my dad is going to live forever. Knowing him he probably will. I don’t know which is worse. Dreaming about him being dead or living forever. God help us all.’
You go out and get off your head. There's free drink and drugs. Then you wake up and people are calling you ugly and fat and what a state you are

When Lily talks it’s like listening to the lyrics of her songs. She is funny, charming, intelligent and honest. When bad things happen she doesn’t expect any help or sympathy. The only person she relies on in life to sort things out is herself. She kicked off her music career on her own, financially she is self-made (worth an estimated ?3 million) and as a woman she is utterly independent. When she’s not talking or trying on dresses or dealing with the alterations man from the dry cleaner’s, she’s sorting out tea for her dapper seventysomething granddad Eddie – Keith’s father – and fixing up an appointment with her doctor. When he begs to demur, she tells him: ‘I don’t trust your doctor because he’s not my doctor.’

In the story of a dysfunctional upbringing, Eddie was one of the few figures of security. Lily’s grandmother, who died last summer, and grandfather spent much of her childhood looking after her and her younger brother, Atonement star Alfie. Her father, Keith, left her film producer mother, Alison Owen, when she was four years old, and it was Alison who then had to work full time to support Lily, Alfie and Sarah, her older daughter by a previous relationship, who is now 29.

Lily was sent away to a number of top public schools including Millfield and Bedales, and was expelled from several for bad behaviour.

‘I hated school,’ she says. ‘I hated being away from home, away from London. I never felt what I was being taught was in any way relevant to my life.

'I’m just not good with authority figures. My mum used to have to work all the time and we’d have nannies looking after me and my little brother. I’d be on the phone all the time saying, “She’s telling me to do this and I’m not doing it.” My mum would just say, “Tell her to shut up then.”

‘It was pretty hard to be a rebel in our house as there wasn’t much you could rebel against. Mum wasn’t into authority and everyone knows what my dad is like.

'I was never really concerned about my future because I always knew I wanted to be a singer. I just believed it was going to happen. I think I am very much a product of my parents.

'I can moan because they didn’t do everything I wanted and it wasn’t perfect, but ultimately I’m proud I’m part of them. They’re different. That made me totally determined and motivated to do exactly what I want. It can be good or bad, but it’s always my choice.’

Eddie remembers things slightly differently.

‘Lily’s had her moments. But she’s still a sweet kid. My wife used to have a tape of her singing in the Millfield school choir, which she’d play again and again. When they were little kids, I don’t remember Lily causing any problems at all. She was the quiet one. It was Alfie who was the terror.

‘Of course, her gran and I are proud of her. Neither of us are very keen on some of the swearing or things she might do or say. But you have to accept it. That’s the way things are today. If you don’t accept it you’ll lose her.’

Lily shrugs. In many ways her unconventional childhood must have been the best preparation for life as a pop star. In between schools, she enjoyed tea at her grandparents’ along with visits to the Groucho and tiny roles in her mum’s movies (she played a member of court in Elizabeth).

‘Yes and no,’ she says. ‘There was always something going on. I remember Alfie being the bad one. There was always some drama with Alfie. You couldn’t compete. Unless you joined in. I think it did change me. It gave me independence and it made me look at authority in a totally different way. Like, it wasn’t ever going to be something that applied to me.

‘What I really wanted was a mum at home all the time, and a dad. It just didn’t happen, though. My mum had to work because she had to earn money. But that’s not what I want for my kids. I just want to be there.’

Lily can easily flick from being daddy’s girl to her mother’s daughter. Ultimately she wants to face up to her responsibilities. It is no coincidence that Lily gave up drink and drugs last September, the month her baby was due.
The other thing she did was disappear to Los Angeles and write a new album, It’s Not Me, It’s You. (‘I had to get away from London. All the distractions, all the parties. I’m not good with temptation so I just had to go.’).

The new recording surpasses her Grammy-nominated debut, Alright, Still in its lyrics and observations. The songs are about taking too much cocaine, party girls, mucked-up love affairs, the grand and the humdrum all wrapped up together.

Much of the album was written at the infamous Chateau Marmont in Los Angeles.

‘I wasn’t booked in there,’ she says. ‘My record company put me in this horrific apartment. I got there, unpacked and then just sort of exploded. I got back into my rented Mini with my girlfriend, piled all our stuff in and drove to the Chateau Marmont.

‘They didn’t even have a room.The guy on the desk told me there was just one vacancy, which was (a bungalow)
in the garden. It was the place John Belushi died in. He asked me if that was a problem. As if…’

Right now Lily is enjoying being clean and sober.
People take drugs because life can be dull. We shouldn't put drugs on a pedestal. Lots of people take drugs and then get up and work

‘I have to have something to do,’ she says. ‘I need to work. I need to be busy. What terrifies me is having nothing to do. I was terrified after my first album because I didn’t know what was happening. I didn’t know when the second album was going to work out. It does literally terrify me. That’s what gets me into trouble. I’m so terrified I need to numb my mind. It’s what I do.’

Lily has had a lot of therapy. Aged 18, she tried to slit her wrists after her first serious relationship ended. She was sent to the Priory.

After her miscarriage she sought help and every now and again she goes to ‘sort myself out’. She is clearly, right now, dealing with her wild streak. Other issues also lurk close to the surface. It’s not difficult to draw parallels between her relationships with men and her relationship with her dad. Lily seems to go for father figures.

‘I do definitely prefer older men,’ she says. ‘They just get me more. They’re more interesting, you know, have more to say, more to think.’

Simons is 39; her most recent ex, Jopling, is 44 and – rather worryingly – a close friend of Keith’s. Lily appears untroubled. You can see she accepts there will always be a chase. There are several mentions of a man called ‘Ricky’.

She is getting dressed up as she’s going to see him in his office. It’s not a relationship but, in her tight black dress and heels, she asks, ‘Does this look… you know… phwoar!’ And she laughs. She likes flirting. It’s up there with eating out, walking her dogs and fancy clothes. ‘But I have to be doing things. I like having a million things to do. Projects, challenges.’

She’s had dinner with Boris Johnson to talk about getting involved in some way with teenage issues. ‘It’s tough being a teenager. We have a terrible education system, there’s a lot of fear, lack of community. I just want to get involved somehow, to do something.’

She is also reading about as many things as she can: art, politics, foreign affairs. ‘I didn’t learn much from school but I’m a massive self-educator. I’m always reading, asking questions, on the internet. If I’m out and someone says something I don’t know I’ll get my BlackBerry and Google it under the table. I’m obsessed with learning stuff.’
In the corridor is a framed copy of her police arrest form following an alleged assault on a photographer in 2007. ‘I love that,’ she says. ‘I had to have it framed and put on the wall.’

You wonder if drugs will continue to be a thing of the past. She shrugs. ‘I’m not saying never. People take drugs because life can be dull. We shouldn’t put drugs on a pedestal. Lots of people take drugs and then get up and work. You can never say never, just not now.’

Lily has worked out that, in the end, it’s all about what you earn. ‘You start out and you just put all of yourself out there. And then you get messed up. So you have to draw back. It all still goes on. But I want to work, do well with this album, get a boyfriend and make enough money to buy a house in the country.’

Does she want this album to be a critical success? She grins: ‘Well yes. But most of all I want it to sell. That’s what it’s all about, isn’t it?’