Ever since she nabbed her first Sovereign ring aged 13, Louise Harman has been on a rite of passage to supreme pop power. Now the tracksuit wearing, pint-sized MC has become a brilliantly charged symbol of a new Britain. From tower block pirate radio to business meetings with Jay-Z, Lady Sovereign is the real deal. Listen up.

The first time I ever saw Lady Sovereign off stage was in an Old Street newsagent. She handed over a crisp fiver in a petite hand to the Asian man behind the counter and asked for ten Sovereign ciggies. As she did it the light streaming in through the door caught her sovereign ring and blotted yellow sunshine allover her beautiful and tiny face. She just oozed essence of sovereign.

Louise Harman hasn't been called Louise for a while now. "Ugh!" she says, practically gagging on her large Pernod and lemonade at the very idea of it. (It is 11.30am: "you gotta, intcha?"). Sometimes her dad calls her 'Lou' but she doesn't like that very much. Even her mum chooses the abbreviation by which she is most commonly referred to in order to address her youngest daughter these days: Sov. Just before she started bunking school regularly at 13 - six years ago Louise stole her first Sovereign ring from her best friend's boyfriend's bedside, because he was being, like, a total jerk to her friend (" a fucking cunt", to be more precise) and "the thing was just sort of sitting there, just sort of winking at me, just sort of asking me to take it, just sort of begging me to take it." So she slipped it into her pocket as her own personal revenge of the sistahood.

When she got home she liked the look of her trophy. Then she slipped it onto her finger. And she liked that feeling even more.

"What is it about sovereigns?," she muses, shyly, as if it is to describe her very essence (which, in some ways, it is). "I dunno, really. It's just that special thing that they have. I looked up the meaning of them and it's something to do with, like, supreme power or something. But I don't really give a fuck. I just love them. It's the look. What it represents is nothing more than what I want to look like."

The sovereign ring might traditionally be something to do with supreme power (or something), but its modern British invocation is as a working class rite of passage. When kids get their first sov it is their token of maturity, of them turning into an adult. Traditionally, it is about boys becoming men, but girls like sovs, too, because they have a weight and glow that says 'special' and the latticework on the band could even be considered a bit dainty. Since first alighting on the power of the sovereign Louise has defined herself by her idiosyncratic choice of personal accessory. She has taken the identity of her favorite ring. She has morphed into her bling. Sov has never been seen without a sov on her finger since. At one time she was wearing five sovs, though even she confesses that this was maybe" a bit much." She doesn't do sovs round her neck on chains, but she understands people who do because "it still looks right." She added the stately prefix before her chosen name as a private joke to herself; her rum, snippy and proud vindication of her upbringing. Lady Sovereign. Even the juxtaposition of the two words that conjoin so beautifully in her brilliant pop monickerÕs enough to prove that she's the best thing to happen to pop music in, like, forever.

There is currently a rumour on the Internet that Lady Sovereign is Melanie "Sporty Spice" Chisolm's daughter. "I love that," chuckles Sov, from behind her yellow highball glass, ice-a-clinking. You can see the thinking. She is the subject of much internetular rumour. Her favourite is that she has five children, all of whom she is scamming benefits for. Rubbish, of course, "but good for the myth". Myths spout up around Sov all the time. People assume her to be rock solid because of her brilliant, street tough performance technique, all intuited from her years in thrall to underground British black music, but she is soft as a doughnut (with a sly irony, her longest standing job before becoming the nation's most-likely-to MC was on a doughnut stand in Wembley, which she gave up after becoming known as "the doughnut girl" at school).

Sov's performance chops are elicited from her brilliant way with a musical motif. In three short years of getting to understand a recording studio, largely under the tutelage of her musical mentor and producer, East London grime ace Medasyn, she has leapt on in bold strides. She cannot now listen to her recorded debut, Make Way For The S.OV., put together for the soundtrack of a low budget Britflick she was picked for at 15 about a young female MC that escapes her estate routes (see the connection?), but it has bucket loads of street charm.

What Sov brings to the musical table now beside her playful disregard for a genre -"I don't do grime, I don't do reggae, I don't do hip hop, I don't do pop, I don't do indie, what I do is just me on a record: we're all a bit bigger than that now. The worst thing someone could say about my album is it's boring" - is humour, fluidity and a nice way with a gargantuan personality. If you were to invent a pop star to exactly fit the moment in 2006, you would almost certainly invent Lady Sovereign.

There are a lot of things that Lady Sovereign doesn't do, but wearing skirts and being called Louise are top of the list. At the same time she decided that school was useless and failing her intuitively bright brain - at the time, in short, when she found her Sovereignty - she gave up skirts.

"They just felt wrong." She has never worn one since (she is nothing if not self-possessed, Lady Sov). Her elder sister is getting married next year and there has been some debate as to whether Sov should be a bridesmaid. "I told her! I said, I ain't wearing a fucking dress! Even though it's my sister's wedding and everything I just can't wear a dress. I don't care. I mean, I do care about my sister and all that but it's just...I couldn't do it." She looks horrified at the prospect of the skirt, worse still the thought of a dress. "I remember being in primary school and wearing little pleated skirts and them long socks, but then one day I just went off a bit, when I started hanging around with the boys and playing football an' you know, doing laddish things? That's when I stopped wearing skirts and dresses and all that." Sov hasn't worn a dress or a skirt "for about twelve years. It's just not me, I tried one on for a joke three weeks ago and I was just like, ugh, this doesn't look nice. I mean, it just does not look nice. It's like putting a dress on a pit bull."

A compromise has been sought over the forthcoming nuptials. Sov and her elder sister are looking for a tracksuit in pale cream, beige, or preferably white for her to follow her big sister up the aisle in. "It ain't as easy as you think," she says. Sov thinks that she will still be wearing tracksuits when she's 60. "Like Jimmy Saville," she titters. Saville - that peculiarly British, cigar-smoking, oddly bleached, velour leisure wear-sporting institution that famously had his voluminous leather armchairs made for him and more infamously was thought to have one of the largest collections of pornography in the land - is Sov's second favourite tracksuit-wearer of all time. "I think he's a legend, man; he might be a bit dodgy, do you know what I mean? But for him to walk around like that was brilliant."

Her favourite tracksuit wearer, predictably, is Missy Elliot. "Fucking lush. Her leather tracksuits are the best tracksuits in the world.”

If only they cam in cream.

It's easy to spit and snarl about chavs, as the new national mood has readily declared. Second only to Muslims in the boiling pot of white British suburban prejudice, estate kids and those that worship the looks they bust are now the pariahs of 'sensible' society, with nary a lone voice to defend their honour. In this climate, the steadfast simplicity of the likes of Sov stand up as almost heroic beacons of a culture that has been made counter through an accident of time and political exchange only. Demonized for the offences only of being partial to a bit of Umbro and an extra-length cigarette, chavs have become the whipping boys of Blair's Britain.

Sov is a brilliantly charged symbol of a cultural moment. This is the way pop stars have flourished in the past, but in a heavily mediated world of investment and post-pop irony where Girls Aloud must trade their own brilliant wardrobes of hoop earrings, cheap tattoos and market velour in favour of looking like slutty TV presenters with matching hair pantones in order to be given a song too complicated for them to sing - there is not much room for those that truly rise from street level up with their own voice remaining intact. Does it even need pointing out that Sov is a breath of fresh pop air in these chillingly calculated times?

Yet she cuts deeper than that, too. Somewhere in the last decade there has been an illusive crossover moment: when street wear and street kids turned into a thing of shared national disgust; when dressing in highly polished bus-stop uniforms changed from being a sign of low-level, cheaply accessed identity and metamorphosed into a thing of terror; frightening the morbid watch guards of Middle England into bolt-upright rigidity. When did a topknot acquire this crazy new level of significance?"

Sov is not superfluous to the demonisation of chav. "Course not. The funniest thing is how posh people can write books about it, taking the piss out of it and make money out of it. How wrong is that? Just targeting the way people like me dress." Do you feel exploited by it?

"What I don't understand is who these people are. Well, I do: they're greasy haired student rockers who can't dress. Posh people can't dress right. They don't know how to do it. So they jump on us to get their little fifteen minutes of fame. I think the books are funny, sometimes. I read 'em. But it is way too stereotypical. They got most of it all wrong."

When Louise Harman kicked school, acquired her high voltage, astringent new look and awarded herself a title to go with the whole new ensemble, she was only doing what millions of kids do up and down the country every day. Rejecting what she was given and finding her own way in the world. A bit of petty theft and scamming was going to have to go alongside her ace new Identity. Louise Harman, see, was not born into privilege.

Sov was born into the Chalkhill estate in Wembley, where she lived for 11 years before uprooting to another sink estate in Neasden, North West London. Her parents were punks. Her dad was the real, fully convincing deal she reckons, but her mum, who she has photos of with a mohawk, homemade piercings and shredded clothes was "just doing it to please him."

Because of her lineage, DIY music is in Sov's veins. She knew about Lee 'Scratch' Perry before she knew about Madonna. Her first favourite band was East 17 - she liked the look - with whom she was obsessed for, ooh, weeks, though she couldn't buy any of their records because money was tight in the Harmon household. Her auntie taped her the album, Steam. ÒInside itÕs raining but outside its wet.Ó She chides herself about it now, needlessly.

When she stopped school, unofficially, she went the regular, timeworn modern truants route. "I sat at home and watched Trisha until it bored me out of my mind." Like every disillusioned London school-kid with an ear to the pulse of their own cultural ascendancy in the last decade, her road to Damascus came with pirate radio. Her first love was the now defunct Mac FM, but she soon graduated to Freeze FM and Lush FM, both operated out of North London tower blocks, just like the ones Sov was non-operational in. She would sit and listen to the MCs for hours, transfixed by their cutthroat approximation of American hip-hop. "It was like coming home," she says now. Before long, the little Lady was calling into the late-night open mic competitions with her own rhymes. She could freestyle almost immediately. "Some people thought I was shit, but some would phone in and say 'who's the little lady? She got something going on.'"

Sov being Sov - five foot one and a bit with the face and skin of a 12-year-old, even now - she couldn't get in to the raves, but she was happy at home and with her friends, tearing up the airwaves from their bedrooms. As the great British underground black music story of the last ten years unfolded, as jungle begat garage and garage begat grime, so Sovereign was there, carefully tracking its journey, thinking what her own USP was to bring to the party. Her first real love was Dynamite:

"Oh she straight away opened doors for me. When I heard Ms Dynamite I was like..."

She was the one?

Sov recently met her formative hero.

"I swear blind I was like... I didn't know what to say. I was like, 'Can I have a hug please?'

I just gave her a hug, it felt so nice just to meet her, because I just think she's wicked, man. Ms Dynamite inspired so many female MCs. 90 percent of the time you ask a UK female MC, my sort of age range, 'Who's your inspiration?' And they will say Ms Dynamite, no doubt about it."

Sov is a fragile mix of dynamo MC and baby girl. There is a startling innocence about her, and sometimes she feels like the music industry is too hard-bitten and cynical for her. "Everyone wants you to work all the time," she bemoans, suddenly the schoolgirl sitting in front of Trisha on her mum's sofa once again, not the independent 19-year-old businesswoman that is being ferried transatlantically by the hottest names in black music to see where they can take her. Two days after we meet she is shipped to meet Jay-Z on business in New York, Pharrell is interested in producing a track for her and Missy would like a meet (of course Missy would like a meet). "When I first heard about it I was on the phone and my manager told me about it and I was just jumping up and down, literally with excitement. I was just like, 'Oh my God.'"

Getting Sov's debut album together has been a labour of love for both her and Medasyn, slaving over the beats in his studio in Bethnal Green. It may take a little longer. The girl with the unrepentant council attitude in a time when it's needed most is glistening right now. I ask her if she has anything else she'd like to impart to the people.

"I just want them to know that I might be a midget, but I've got a big voice. It will be heard."