Lianne La Havas - Her voice is big enough

"I cried. It was something I'd wanted and dreamt of but you have no idea until you're told and I was just so, so, so… happy." Lianne La Havas is recalling the moment she found out that her debut album, Is Your Love Big Enough?, had been shortlisted for the Mercury Prize earlier this month. "It's been such a great summer. It's interesting that I consider there to be quite a lot of pain discussed on the album and now I'm just really happy all the time so I'm like, 'God, what am I going to do for the next record?'"

Sadness is something of a speciality for the 23-year-old Londoner. With her unique blend of soul, folk and jazz, La Havas's personal tales of falling in and out of love, sung in an impressively smoky voice that goes from a purr to a roar in an instant, are somewhat reliant on a certain kind of temperament. Not that she's too worried about the next record.

"There are so many different things that you can draw upon and angles that you can look at things from in song," she says, sipping on coffee in an east-London café.

Since coming to the public's attention last October when she appeared on Later… with Jools Holland, before she'd had a single release to her name, La Havas's rise to the top has been seemingly effortless. Her fellow guest on Later…, Bon Iver, was so impressed with La Havas that he invited her to join him on his north American tour. She was featured on the BBC Sound of 2012 poll at the beginning of the year. Stevie Wonder has turned up at her gigs and left her voicemails of encouragement. Her album charted at No 4 back in July. And now the Mercury nomination. No wonder she can't stop smiling.

Her Greek father and Jamaican mother split when she was just two years old and she was raised predominantly by her grandparents. However, they all instilled in her a love of music. But, although she had been part of the school choir and completed a GCSE in music, it was only upon leaving school at 18 that she decided upon a music career. She decided to get in touch with an old schoolfriend, the singer Rox. She became one of Rox's backing singers, before doing the same job for Paloma Faith.

"I loved being a back-up singer, I think it's a really great job," she insists. "I was lucky enough to have the time to be working on my own stuff, and I just wanted to feel ready when it came to that point of doing my own thing."

It was around this time that she picked up the guitar, mainly because a lot of people in her new musical circle could play and, being more portable than a piano, thought it would be good to accompany herself on when she worked on her own music while on the road. Things began to snowball after she posted some early songs online. Music-industry execs started to circle, she got a manager, was introduced to Matt Hales, of Aqualung fame, who became her writing partner, and then she was offered a development deal with Warners in 2010.

But she has been faced with setbacks and there were moments when success seemed far from assured. "There were a lot of times when I couldn't write anything," she recalls. "After I decided to leave Paloma, there were times when I thought, 'God, why didn't I just stay in the band?'. I was completely broke and not able to write, and people at the label I'd been working with had left and there was this kind of limbo. I felt like I had lost all my momentum." She decided the only thing to do was to play as many gigs as possible. "I just played and played and played. I kept playing because I was frustrated," she says. "Then somehow I managed to create some sort of buzz; I don't know how it happened really."

The buzz led to her being invited to perform an internet Black Cab Session, which grabbed the attention of the Later… producers. Now La Havas is in a position where breaking America doesn't seem out of the question. She's already had a positive write up in The New Yorker, was a hit when she made her US television debut earlier this month on The Late, Late Show with Craig Ferguson, and has some more gigs lined up there later this year. But for now she's focused on next month, which will see her embark on her biggest UK tour to date, and, of course, the Mercurys.

So, who would she like to see win? "I'm so happy that Jessie Ware is nominated. And I happen to know her and just love her singing and love her songs. So it would be amazing if she won. The talent on the list is insane. Yeah, I would vote for Jessie," she says, before laughing. "I mean, only if I couldn't vote for myself."

Lianne La Havas tours the UK from 5 October. 'Is Your Love Big Enough?' is out now