The Welsh singer thinks she’s coping well with her sudden fame.

It’s Friday, so it must be Germany. Duffy is having “an extremely hard morning” reaching out to the European demographic, wading knee deep through all the promotional mulch that must be negotiated prior to the release of her new album, Endlessly. As she puts it, not entirely delicately, the singer has just spent the past few hours “being probed by German journalists wanting to know everything about my life”.

Probe they might, but I suspect she’s a woman who has learned not to give too much away. Fame does that to you. When I tell her later that Endlessly sounds like the work of someone who has been through the emotional mill, she laughs but veers away from a direct answer. “Through the emotional mill?” she ponders. “Isn’t that what women do anyway? Isn’t that how we spend most of our day?”

In fact, Duffy today is full of energy and excitement, buoyed by a burbling vivacity which seems genuine. Rarely far from a full-throated laugh, at times her voice drops to a soft, conspiratorial flutter; at others she merrily plucks her words out of thin air. In general – pesky German journos aside – she seems thrilled to be back in the fray.

Over the past three years Aimee Ann Duffy has metamorphosed from an unknown northwest Walian into a global superstar. Spool back to November 2007 and her name was just beginning to rise on the lips of critics heralding her as the Next Big Thing. With her second single Mercy and her debut album Rockferry, released in March 2008, she quickly sealed the deal.

A clever, contrived, ruthlessly commercial yet heartfelt patchwork of 1960s pop-soul shapes, Rockferry invited comparisons between Duffy and everyone from Lulu to Dusty Springfield. Its success wasn’t merely a local skirmish. Rockferry was a top five Grammy-winning album in the US and in Britain spent an entire year in the top 10. It has sold over eight million copies worldwide, and this in the dying days of the recording industry. I make that eight million reasons why Duffy’s life must have changed beyond all recognition.

“Not really,” she says. “Wouldn’t it be great to say yes? But not really. I think I’ve kept things in perspective. Of course, everything unravelled after the success. Everything always unravels, but that’s the way life is. My life always has these chapters that unravel.”

In the slipstream created by Rockferry’s impact, Duffy clearly experienced a few wobbles. She had difficulty adjusting to being recognised in the street, and caught considerable flak for advertising Diet Coke perched pertly on a push bike.

“If I’m being honest, I really didn’t think I’d be talking to you right now,” she says at one point. “It was possible you wouldn’t have heard from me for a few more years.” She talks about how she planned to “buy a house and disappear”, retreating to the sea, seeking anonymity in the wide open spaces. “I wanted to withdraw, I wanted to pull myself away from it all for a while,” she says. As it was, after coming off the Rockferry tour she did indeed buy a new house, but she only spent a week moving into it before taking off to make a new album.

Having worked on Rockferry with former Suede guitarist Bernard Butler as her producer and co-writer, on Endlessly she swapped the man who wrote Animal Nitrate for 66-year-old composer and producer Albert Hammond. As well as being the father of Albert Hammond Jr, the guitarist in The Strokes, Hammond is the man responsible for The Air That I Breathe, When I Need You, To All the Girls I’ve Loved Before and dozens more fromage-fragranced MOR staples.

It doesn’t seem, on the face of it, a terribly obvious creative partnership. Hammond’s wife had seen Duffy singing Stepping Stone on US comedy show Saturday Night Live and called her husband into the room. Although he had effectively been retired for the past few years, Hammond loved her voice and requested a meeting. Almost immediately, they began writing together.

Did she even know who Hammond was initially? “I remember my mum singing When I Need You doing the ironing,” she says. “But you don’t think, do you, about the person who wrote a song like that? It’s a shame, but it never crossed my mind to think beyond the song. It’s almost like it transcends humanity, like it’s always been there.”

The pair met up in January 2009, just before the Brit Awards, where Duffy picked up three trophies.

“Albert caught me at a point where I really wasn’t thinking about the next record,” she says. “I’d just hit that milestone, everyone was going, ‘Wow, five million record sales in less than a year’. Everything was kicking off and I wasn’t really thinking about more material, but he intuited that it was perfect timing. So it was like, ‘OK, let’s give this a whirl.’”

She had to wrestle with the traditional dilemma facing any singer who has experienced a colossally successful first record: follow that. Starting work on Endlessly, it must have been daunting to have the shadow of Rockferry hanging over her.

“Honestly, no,” she says. “It felt that the natural phase of the success of Rockferry had gone. There was new material, we had 25 songs written, and it was all part and parcel of moving on. It came together so seamlessly, there really didn’t feel like a moment of contemplation. Albert was so experienced, so wise, so fun, he made it all so easy. Sitting down and writing songs with him was a piece of cake.”

Endlessly gives Duffy a sleeker, more contemporary upgrade. Her voice, with its helium vibrato more pronounced than ever, will still divide listeners, but the songs are, if anything, even stronger than those on Rockferry. The rhythm hits harder and sharper on the upbeat tracks, which include some winning excursions into Abba-land. The ballads, meanwhile, are less orchestrated, more open and direct, with real emotional clout behind them.

Duffy may have been stepping out with Welsh rugby player Mike Phillips for the past year, but the album speaks eloquently of vividly recalled turmoil. You can hear the unmistakable twinge of raw nerve endings and severed heart strings.

“I was searching for this purity, this vulnerability, this naivety,” she says. “Both Albert and I in our own little way, 40 years apart, were fighting for that. The problem is I’m a perfectionist. I’m a control freak with my music. I long for quality. I yearn for it, I search for it, it has a hold on me, but I can over-think things. I wanted this to be real and raw.”

Now 26, Duffy has certainly developed as a writer, a fact she attributes to the support she has had from collaborators like Hammond and Butler. “I appreciate the room I’m given to say so much,” she says. “It would be easy to snatch the pen off me and say, ‘No kid, let us do the writing for you’, but people I’ve worked with have been interested to see what I bring. It wasn’t so easy years ago, I didn’t get any room. I remember being 16 and meeting writers and feeling quite censored. I’ve had to wait with diligence.”

Another reason Endlessly sounds so fresh is that it features The Roots, Philadelphia’s legendary jazz-influenced hip-hop band whose snap and crackle keeps the record rattling along. Their presence was another case of divine intervention via cathode ray tube. Hammond saw the band playing on television – “I think his entire career is down to sitting in front of the telly,” giggles Duffy – and suggested that they use them as the backing group. Unbeknownst to Hammond, Duffy was already a huge Roots fan, and had given drummer Questlove a copy of Rockferry in 2008.

She clearly gets a kick out of these serendipitous touches. Perhaps Duffy has discovered over the past three extraordinary years that it’s healthier to attribute fame and fortune to the vagaries of chance. “There’s an expression ‘spitting in the wind’,” she says. “I feel that’s how I live my life: spitting in the wind, living on the edge, putting it all to fate and seeing what happens.” She laughs happily. “It’s quite extreme.”