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In the market-stall bustle of Golborne Road, West London, there's nowhere for a people carrier to stop. With hazards on, the driver of one such shiny black vehicle double-parks outside the offices of Rough Trade Records and delivers two huge baskets of cupcakes. Ascending from the basement offices, Duffy emerges to see what all the fuss is about. No explanation is needed that the cupcakes - covered in Stars-and-Stripes icing - don't already convey. The day before our rendezvous, Duffy's debut album Rockferry leapt straight into the US Top 5. Last week she was shortlisted for three Mojo awards, the winners of which will be announced today. Though managed by Rough Trade, Duffy is signed to Universal, which has sent the cakes by way of celebration. Smaller than you probably imagined, with kohl-smudged Lisa Simpson eyes, Duffy dives in and reduces one to crumbs. Then she lets slip what those who work with her have taken to calling a Duffyism - a hitherto nonexistent word that nonetheless sums up the situation perfectly. “It's a bloody worldwind, I tell you.”

Fame may be a new experience for Duffy, but she shows no signs of struggling to make the adjustment. Being recognised, she says, is fine as long as people don't address her by her first name, Aimee. “The only people who do that are complete strangers. There's no better way to make me feel uncomfortable.” Recently, in Seattle, she found herself addressed as Aimee, by “a fan who wanted to get a little bit on me”. Duffy visibly cringes at the encounter. “She had been to Wales, seen Llandudno, done it all - the whole Duffy tour.”

For the record, she says there's no better way of becoming familiar with her than to call her Duffy. “Everything I've ever done as a singer has been in support of that name. It's my integrity.” Nevertheless, it's worth adding that her one EP, two years before the release of Rockferry, was made under her full name. Some critics have highlighted the difference between Aimee Duffy, the aspiring Welsh power balladeer of songs such as Cariad Dwi'n Unig - and the artfully executed retro-soul of tunes such as Serious and the chart-topping Mercy. The implication is clear. She may be managed by Rough Trade, but the transformation smacks of slick marketing. In Duffy's defence, it might be pointed out that her musical development is not unlike that of the singer to whom she has been mostcompared. Who in their right mind would choose Dusty Springfield's twee folk-pop work in the Springfields over Son of a Preacher Man and Spooky?

Duffy's drive is all her own, but she divides the credit for her progress between herself and the woman at Rough Trade who mentored her - Jeannette Lee, the former Public Image bassist. Bernard Butler, producer and former Suede guitarist, remembers receiving a call from Lee about her new find. He took her to his local Crouch End eatery, shrinking into his seat as the new girl, alone in the big city, attempted to engage the surly London waitress in conversation. The following day, Butler played her a chord sequence “for a song that would have no chorus - just a series of verses that go higher and higher, way above what Duffy believed to be her actual range”. Butler recalls that Duffy then began to sing about a place in America that she had never been to. “I told her to space the words out and tell me about a place she actually knew. That's when this place, Rock Ferry, near North Wales, came out of her mouth.” Within a few hours, Duffy had recorded the vocal for the title track of her album. Jeannette Lee remembers that both Duffy and Butler were both taken aback by the speed with which a song appeared.

“Bernard took her out of her safe zone,” recalls Lee. “He made her feel quite uncomfortable at this point. She had been to London only a couple of times and, really, she came away from that session totally confused. He knew it was something out of the ordinary. But whether it was good or bad, he wasn't sure. I was gobsmacked, though. I played it five times in a row. Just totally gobsmacked.” As Lee puts it, Rockferry was the song that shone a light on Duffy's future direction, turning her from ingénue to star. Duffy says that she knew from an early age that she could sing and that she was serious about it. If school held little interest for her as a teenager, perhaps that was because her life seemed a little too grown-up for formal education. After her parents separated when she was 10, she moved from Nefyn in Gwynedd - the town where she was born - to live with her father in Pembrokeshire. By 13, she had her first job at a seafood restaurant, earning £150 a week. “They were patient with me,” she recalls. “I kept telling people that the special was lobster Benidorm when lobster thermidor was what I meant.”

After waving goodbye to Twnti Seafood, there followed a series of college courses and, somewhat randomly, a plan to go to Switzerland and become a writer - this in contrast to her family's preference that she train to become a nurse. In 2003, on the eve of her departure though, she was sounded out about appearing on the Welsh version of The X Factor - Wawffactor. Looking back now, she says that staying to compete in the show (she eventually came second) made her “very unhappy”. Every time she advanced into the next round, she would have to travel south to Cardiff - a nine-hour journey on the painstakingly circuitous Welsh Traws Cambrian bus. “I hated it. They tried to dress me up like a transvestite, with make-up on about this thick.” She holds her forefinger about an inch away from her thumb. Enter “Aimee Duffy” into the search field on YouTube and you'll see that she isn't exaggerating much.

But by the time Wawffactor aired, Duffy had met Lee. The woman who Duffy now cites as her closest ally may not have known what she would go on to become, but she knew she was some way off from being a pop star. Not that Lee had much of a greater game plan. As she put it: “Duffy was this girl with a great voice, who I sometimes gave money to record demos.”

Duffy and Lee have good reason to remember January 24, 2006. Staying in London for the second time, Duffy was asked by Lee if she wanted to see The Strokes at Shepherds Bush Empire. Struggling to get to grips with the London Underground, she boarded the wrong train and ended up miles from the venue. By the time, she arrived at the show, The Strokes had only two more songs to play. Duffy says she was flustered at the prospect of meeting “proper record company people” in a social situation. This doesn't quite tally with Lee's recollection. “I just remember, coming to her seat, that she had a look of absolute wonder on her face, like there was a neon sign above her head saying, ‘I'm going to play here'. She was blown away - this combination of naivety and confidence.” Finally, two weeks ago - as Duffy's biggest headlining tour to date took in London - Lee's premonition finally realised itself. Duffy sang before a sellout audience at the venue she had barely managed to find as a newcomer to the city. The evening of the Strokes show was also when Duffy get the idea for her current hit. Had it not been for the tourist-bewildering Edgware Road interchange, she wouldn't have mistakenly emerged at Warwick Avenue and promptly named a song after the station. Perhaps it's no surprise that a song born at such a time of upheaval should still stir strong emotions.

A video storyboarded for the song, showed her getting out of a cab to find herself amid a street party. In the event, almost none of it was used. Climbing into the cab for the first scene, and hearing her own song pipe out of the speaker, Duffy began to mime, as instructed - then found herself unable to stem the tears that followed.

What happened over the next few minutes is what we see in the video of Warwick Avenue: the attempt to carry on, a moment where it seems she can't continue, the lone weeping in the back of the cab and then a frail rallying to the end. “That song,” explains Duffy, “has the ability to...I mean, when I'm singing it live, I can control it. I just remember feeling really embarrassed - like I really f***ed up that scene. Then I went to see the edit and Daniel [Wolfe, the director] was white like a ghost.” Jeannette Lee remembers being in the editing suite. “I think we were all shocked. Then the question became, ‘Which version do we use? The street party one, or the crying one?' There was no contest. One was an advert and the other was the real thing.”

Duffy doesn't talk about the relationship that prompted the song - although she says that the men in her life have not given a good account of themselves. She's now negotiating a tricky transition. A platonic relationship is turning into “something more”. That's fantastic, I tell her - although that's not necessarily what she wants to hear.

“Yeah, but I don't know. I'm a commitment-phobe. Why? I don't know...It's the only thing I'm afraid of.”

Maybe it stops being scary when you have met the right person.

“It's tough. It just scares me...all of that stuff.”

What about when you're alone in the house or a hotel. Do you feel comfortable dressed in one of his old T-shirts watching some crap telly?

“We're not really at that point,” she says. “I just don't know. And besides, I'm really happy on my own. Because, that way, no one can hurt you.” For reasons that only she may be aware of, Duffy thinks that being unguarded about your desires amounts to asking for trouble. A long time ago she decided that if she told everyone she wanted to be a singer, “they would put blocks in the way to stop me doing what I needed to do”. She adds that “it's the same with love. The reason I don't have it in my life is because they're only going to hurt me.” While her career snowballs, it might be useful for her to believe that, if only not to upset the creative equilibrium. However, in five years' time, I suggest it would be a shame if she felt she couldn't have both.

“That's deep,” she says, in a manner that suggests the subject is now closed. Right now, almost every available hour is taken chasing her own “worldwind”.

“I'd be lying if I said it wasn't exhausting sometimes. But I don't mind a bit of graft.” She recounts a conversation that she had on a plane with someone from the record company. “We went on the plane in the middle of a promo trip and they said, ‘That's the West Coast done'. I said, ‘Just another three to go now'.”

It was left to her fellow travellers to gently tell her about Canada and Mexico - the two pieces of land topping and tailing America. “And I was like, ‘What? There's only two coasts in America'? That's embarrassing for me.

“At the same time, I was delighted. Less work, you see.”

Duffy is at Glastonbury on June 28 and Somerset House on July 18. Her next single, Stepping Stone, is released on August 25

Thumbs down: Duffy is amiable but fogettable
says Sophie Harris

Let's cast our minds back to Duffy's first TV performance, on Later with Jools Holland earlier this year, just before the media furore heaved into action. The lights came up and seemed to gleam off Duffy's perfect blonde beehive, the camera kissed her immaculate eyeliner and her voice fluttered in perfect tempo. And it was, well, kinda scary.

Because Duffy is the 100 per cent antithesis of Amy Winehouse; physically fit, no (apparent) mental dysfunctions, no question her vocal performance will be solid. She's even nominally unthreatening - fluffy Duffy, to “Wino” Winehouse.

While Winehouse's behaviour is frightening in other ways, as an artist it's precisely her flaws that make her interesting - and she has an eerily brilliant gift for writing songs. One cannot fabricate this. And yet the marketing men, again and again, successfully launch slick, robo-versions of a rock‘n'roll original: see Herman's Hermits to the Beatles, the dreadful NSync to Take That, or Stepford skater Avril Lavigne to Gwen Stefani's convincingly smelly No Doubt.

In fairness to Duffy and her record label, 1960s pop was never “authentic” in that there were always svengalis, shadowy songwriters, clever arrangers, behind the singers. But within that, the real greats were those women who channelled their soul into the music. Women such as short-sighted, nervous Dusty Springfield, or pudgy teenager Aretha Franklin. These are the singers whose music sounds as fresh as if it were recorded yesterday; not aimiable, forgettable Duffy.

Thumbs up: give her some R-E-S-P-E-C-T
says John Clarke

Is it just me, or are we living through a golden period for British girl singers?

And by girl singers, I don't mean the dreamy-eyed students talking to the trees. I mean, to forgive the allusion, girls with balls. Vocalists such as Joss Stone (although she might have lost her way a bit recently), Amy Winehouse and now Duffy, who can take a song by the scruff of the neck and make it stick in your brain by lung power alone.

In a field that in the past was occupied nearly exclusively by black singers such as Loleatta Holloway, Mavis Staples or Irma Thomas (Dusty Springfield, of course, being an honourable exception), these British women are able to sing from the soul in a way that the James Blunts of this world just cannot. Stone did it on The Soul Sessions album, Winehouse does it with Rehab and tons of others, and now Duffy is able to infuse songs such as Mercy, Rockferry and Warwick Avenue with an intensity and soulfulness that's neither forced nor false. Critics who accuse her of layering on the emotion as thickly as Dusty did with the mascara aren't listening closely enough.

In the words of the original queen of soul, give the lady a little R-E-S-P-E-C-T.

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