Leona Lewis, the chart-topping pop star who wants to give it all up to sing opera

Simon Cowell's biggest 'X Factor' success tells Adam Sherwin that despite 20 million record sales she’s still not satisfied

Now an international star, Leona Lewis is the most successful winner of Simon Cowell’s X Factor (Charlie Forgham-Bailey)

Popstar to Operastar is already a hit talent show. But for Leona Lewis, the singing star who first unleashed her four-octave vocal range as a nervous hopeful on The X Factor, it is a career transition she now plans to make for real.

“I would love to sing opera. I trained classically and that's what I really wanted to do,” says the Hackney singer, 27, the most successful graduate of Simon Cowell's talent show, with 20 million sales under her belt.

This will be no album of Il Divo-style cod-operatics. A single-minded artist, willing to air controversial views about animal rights and the gentrification of her East London neighbourhood, Lewis is ready to put pop stardom on hold in order to train up for a serious concert-house role.

“I'd love to sing Lakmé,” she says, alighting on an 1883 opera in French by Léo Delibes. Set in India, Lakmé is the tragic daughter of a Brahmin priest. “To sing that role would be a dream for me. But it's a different way of using your voice I would seriously have to commit at least a year for the training. That's how I am. I'd have to go in full-on if I did it.”

Since winning the 2006 X Factor, Lewis has established herself as a global star, topping the US charts with her debut album Spirit and drawing comparisons to Whitney Houston through her lung-bursting, emotionally raw ballads. “Whitney has always been a big influence on me. She passed away when I was recording the new album which was really sad,” she acknowledges.

Although she is no Whitney-style diva, Lewis is willing to stand up for her principles, in contrast to more pliant reality show winners. “I'll never go against my morals,” states Lewis, a vegetarian currently upgrading to veganism, who recalls how one fan made a big mistake when she approached her for a photograph.

“She was wearing a big fur jacket and she was like 'can I get a picture of you?' blah, blah. I don't agree with killing animals anyway but for fashion - I think it's cruel, just so barbaric.

“I see some people wearing fur and sometimes I can't help but be angry. This girl came and stood next to me and I was just like 'Sorry, I can't. I do not agree with what you're wearing right now and it's making me feel sick.' She was so offended.”

Speaking in her quiet, determined voice at a recording studio in north-west London, Lewis sounds surprised at the vehemence of her outburst. “I react before I think,” she admits.

That volatility percolates through her new single, Trouble, released today and the album, Glassheart, out next Monday. Trouble, written with Emeli Sandé, tells of a destructive relationship (“I told you never to get used to me, I stay awake when you fall asleep, I'm a whole lot of trouble”).

Lewis says: “This album has got very bitter-sweet songs about break-ups and relationships I've been through. The drama and the break-ups do feed great songs but so does love. You need both sides of the spectrum.”

She made Sony Music delay the album's release for a year. “I wanted to make sure it was right,” she said. “It's my third album so I was taking it very seriously. Every single song has been fine-tuned and crafted. I'm really proud of it. I want it to be timeless and remembered.”

Even Simon Cowell, who continues to guide the career of his greatest discovery, and spent his St Tropez holiday choosing singles from Glassheart, occasionally has to defer to Lewis. “I definitely take on board Simon's opinion and what he thinks is best,” she says. “His vision for me is very similar to my own. Usually our decision is the same.”

Lewis lives by a moral code instilled by her parents, a Guyanese father Joe and a Welsh mother, Maria. She was brought up in a large extended family and witnessed the deprivation and criminality to which many of her brothers' friends succumbed.

She returned to Hackney before the Olympics and joined the rapper Plan B to work with the borough's youngsters on a music mentoring programme. “I wanted to give a little bit back to the area I lived in,” she said. “I worked with girls who had a lot of strife. One girl had been bullied and wouldn't make eye contact with anyone. They had a lot of issues at home.

”I didn't come in saying 'Hi, I'm going to change your life'. I wanted to give them a project they could work on and give them some skills in music. To give them something to focus on and aspire to.“

Lewis believes a lack of stable role models for troubled teenagers is a big issue and urges more “big brother/big sister” mentoring projects to prevent a return of the rioting which scarred Hackney last Summer. “I think funding those projects is really important,” she said. “I'm sorry if those projects are being cut because they will see the impact on young people.”

She feels torn by Hackney's regeneration. “I love the area and it looks better. But a lot of locals and businesses are being pushed out because of the rents so it's a double-edged sword.”

These days Lewis gets to spend much of her working life enjoying the California sunshine. She doesn't want to leave London for good but finds tabloid speculation about her private life trying. Currently single, she was recently “linked” to Liam Payne of boyband (and coincidentally labelmates) One Direction.

“I don't mind letting people in a little bit but I have learned from the past not to talk too much about my relationships and to keep things as private as possible,” she says. “My animals, my friends and my lovers, they are the most important thing to me. People might pry but I don't let them in because it's sacred to me. They don't need to know my business.”

She also knows that even the biggest stars need the X Factor's ten million-strong audience to sell records. Lewis overcame her reservations to return to the ITV show as a guest judge. “I was dubious. What right do I have to sit on a panel and go 'Yes,no,yes,no.'?

“But I got on the panel and I saw how interested the contestants were with what I had to say. They were looking to me for a reaction, more than the other judges in a way. I felt validated to be there.”

Could she join the judging panel full-time? “Possibly, I feel like it would be quite emotional though. It depends if I could really focus on it. I'm quite competitive - I'd have to win.”

Whether she succeeds in making the shift to opera or not, Lewis is determined to bring a broader range of influences to her music than the charts, filled with formulaic dance-pop, currently allow. “I love Kate Bush, I also like Tracy Chapman. I like soulful, folky styles. David Bowie is such a big influence to me. Everything about him as a person is intriguing to me.”

She will continue to turn down lucrative offers to endorse leather bags, shoes and accessories and use her income to support animal rights charities, maintaining a belief that “maybe in a thousand years no-one will eat meat anymore because they will realise how barbaric it is.”

Leona might be the pop star least likely to follow Lady Gaga and turn up at the MTV Awards wearing a dress made of raw beef - “I thought, that must have been so smelly -but each to their own”. But she has her own code which she will continue to abide by. “It's important to stay true to yourself and what you love,” the singer concludes.

Trouble is out today. Glassheart is released on October 15.

Quickfire questions

Where was the last place you went for dinner?

Annabel's (Mayfair private member's bar and restaurant)

What was the last album you bought/listened to?

Muse, The 2nd Law “I really like the single Madness”

What was the last book you read?

50 Shades Of Grey “like everyone”

What was the last gig/concert you attended?

Paulo Nutini

What was the last sporting event you attended?

A local showjumping event. “I ride and have my own horse, called Spirit”.

What was the last TV show you watched?

“Homeland, it's so good, really enthralling”.