Kirsty Bertarelli performing as a support to Mick Hucknall and Simply Red at Edinburgh Castle in 2010.

Kirsty Bertarelli performing as a support to Mick Hucknall and Simply Red at Edinburgh Castle in 2010. Photo: Getty Images

Extraordinary things happen to Kirsty Bertarelli's pretty face when you ask her about her wealth. A moment previously she'd been chatting animatedly but, as soon as I mention money, her translucent eyes narrow, her high cheekbones tense, her full lips quiver. Her hands shake slightly as she grasps her soy cappuccino.

I feel unkind for making us dwell on such a vulgar topic, but I can hardly ignore it. Bertarelli is the richest woman in Britain, her fortune far exceeding that of, for example, the Queen, JK Rowling and Slavica Ecclestone.

She and her husband, pharmaceuticals heir Ernesto Bertarelli (the fifth richest man in Britain according to the Rich List, and the richest in Switzerland), are worth an estimated £6.87 billion ($A12.45 billion) and divide their time between an £8 million estate in Gstaad where ponies and llamas roam, a £10 million mansion in Geneva, and a mews house in Belgravia.

Kirsty Bertarelli with her husband Ernesto and their daughter Chiara.

Kirsty Bertarelli with her husband Ernesto and their daughter Chiara. Photo: Belinda Rolland

It's an "amazing" life, as Bertarelli, 42, from middle-class Staffordshire origins, admits. Her Instagram feed is full of envy-inducing photos of her in various exotic locations posing in skimpy swimsuits on her yacht Vava II, a £100 million 40th birthday present from her husband (there was also a $US3 million birthday party). They yacht is the largest ever built in the UK and includes a "fold-down beach club" (there are snaps of guests doing yoga on the deck), a helicopter pad and a swimming pool.

One moment she's playing golf in Hawaii, the next enjoying sunsets in the Alps, while her Italian-born husband, 48, is pictured skiing and windsurfing. Beside the photos, old Chelsea buddies such as Emily Oppenheimer and Lisa Tchenguiz make comments such as "Show off" and "U haven't changed. Still remember u dancing on the gold palm trees in the Cave".

But inquiries about these activities - not to mention the private jet and couture wardrobe - are not welcome today, because I'm not meeting Mrs Bertarelli but her alter-ego, singer-songwriter "Kirsty", who's launching her first British album, Indigo Shores.

We're sitting in a cafe near my house in west London, Bertarelli's "people" having disappointingly vetoed my suggestion that we meet in one of her residences. A Jaguar is parked outside, chauffeur waiting in the sunshine; there are almost certainly bodyguards.

Similar-looking to supermodel Gisele Bundchen, Bertarelli is tanned and discreetly made-up. Her wavy hair is much darker and lips less puffy than in photos charting her Eurotrash past - presumably part of the campaign to be taken seriously. Her outfit is hippie chic: flared jeans, a loose chiffon shirt, an unblingy rope of pearls hanging around her neck.

She's friendly, especially when discussing her children, and laughs often, but the Instagram party girl (at New Year she's in a skimpy slave-girl costume grinning into the camera) is absent, replaced by a wary woman, who answers most questions in platitudes that remind you she's a former Miss UK.

"Kirsty's surrounded by jealousy and negativity," someone close to her explains. "It makes her very defensive." Comments on her YouTube page attest to that. "Her husband must have paid a fortune to go along with this," is a typical comment under a video of her duetting with Ronan Keating. Has she learnt a strategy to cope with the barbs? Bertarelli tenses. "Yah, I have in a way," she says in her oddly Australian-tinged voice. "People have preconceived ideas, but the music is part of me. It's not like I woke up one day and thought, 'Oh, I'll be a pop star.'?"

True, before marriage Bertarelli was striving to make it as a singer-songwriter (though contemporaries also remember her as a girl about town). In 2000, she wrote the song Black Coffee, which a record producer approved but then refused to let her record, instead "giving" it to All Saints, stellar at the time, who took it to number one, bringing her £12,000 in royalties.

"Hearing my song on the radio brought mixed emotions," she says, smiling. "I have to be thankful to All Saints, they were so popular at the time they could make the song number one, but I knew the emotions behind that song. I wanted to sing it myself because there'd have been real meaning behind it, which was my love for Ernesto." Passionately she declaims the lyrics. "'I wouldn't want to be anywhere else but here, anywhere at all'; that was how he made me feel." She did, however, sing it in a Valentino gown in front of 250 people at her Geneva wedding. "Yah, I reclaimed it!"

Bertarelli's story isn't exactly rags-to-riches. Born Kirsty Roper, she grew up in Stone, Staffordshire, the youngest daughter of a businessman who, with his brothers, owned Churchill China, one of the world's major manufacturers of ceramics. "It was an amazing childhood," she confirms. "We had so many opportunities: riding, tennis. We were taught good values; in the holidays we worked in my father's factory. It taught us to be grounded."

She was, she says, a "sensitive, emotional" child, always writing "little snippets of poetry" and appearing in local musicals. She boarded at the now-defunct Howell's School, in north Wales. "It really did feel like a separation, I really didn't want to go, but then ... I made some good friends and we're still in touch. I mean ... it's difficult to see them, but we stay in touch on Instagram."

The summer after she gained seven O-levels, she became ill with bacterial meningitis. Her parents - to whom she is close -- discovered her collapsed; doctors said if they'd come an hour later, she'd have died. The scare made her decide not to continue her education. "A near-death experience does heighten what's important, and I knew I wanted to write."

While trying to enter the music industry, she joined a model agency, which entered her for Miss UK, part of her past she refuses - admirably - to disown. "I thought the whole beauty pageant thing was quite funny; I didn't even realise I'd won - I thought it had gone to Miss Mansfield," she says. "I remember waking up the next morning feeling excited about it."

She went on to win £1000 as "second runner-up" in the 1988 Miss World and continued modelling in advertisements and for catalogues. A trust fund bought her a flat in South Kensington and a place in the glossy Sloane set. For two years, she lived with casino heir Damian Aspinall in Belgravia.

At 26, she met Ernesto Bertarelli at a dinner party in a Sardinian villa. With his sister, he had just inherited Serono, the pharmaceutical company founded by his grandfather. Between 1996 and 2006, he more than doubled Serono's revenue to $US2.8 billion, by changing its focus from pharmaceuticals to biotechnology, largely thanks to its discovery of the multiple sclerosis drug Rebif. In 2007, the family sold the company for £9 billion, since then investing in everything from property to drug companies, and philanthropy.

"There were so many girls wanting to be with him and I think he just found me... naively refreshing," she says. "All I wanted to do was sing and be successful; I had this drive. He wouldn't like it if I was shopping all day - but that's just not me." But, for a period, personal ambition was put to one side. "I was swept off my feet. Ernesto's such an achiever; he really goes for it in business and sport and I wanted to be part of the action. I follow him everywhere, whether it's diving in oceans or jumping out of a helicopter to ski, when I'd only skied twice in my life before."

Still, Bertarelli continued writing, and had just won a record deal with Warner Bros. But on their honeymoon, she became pregnant with her daughter Chiara, now 13. "We were on a safari run by Maasai warriors; we were in tents and we didn't actually see many animals, it was a bit of a disappointment. Then we went to Mauritius - but Ernesto had failed to notice that July is the rainy season, so we spent a lot of time indoors, hence nine months later the baby," she says, giggling.

And so, like millions of women, motherhood put a stop to Bertarelli's career. Two more children, Falco, now nine, and Alceo, seven, followed. Then there was the distraction of the America's Cup, the world's most contested (not to mention costly) yacht race, which Ernesto's team, Alinghi, won in 2003 and 2007, meaning the family had to relocate for months first to New Zealand, then to Spain.

"The music industry's very tough, there were all these changes and takeovers at Warner Bros. and at that time I was overwhelmed with motherly love, I only wanted to be with the children, plus I was devoted to supporting Ernesto. But my passion for music never stopped. It was a torment; I remember feeling like something was missing from my life. It's hard to find the time to write songs, though. A lot of them I compose in the bath - it's the only place where I can lock the door and the children can't interrupt."

The couple are clearly devoted parents. Ernesto has said he's determined to be closer to his children than he was to his own father. "His father was away a lot, working excessively, so he and his sister were quite often alone, brought up by their mother - who's a remarkable woman in her own right - while he built up the company. But we're a very close-knit family; I had that upbringing and it really was what I wanted to achieve for my children, though it's slightly more difficult..." she trails off.

"We don't have a nanny anymore," she continues. "I don't want one; I didn't have one. Ernesto and I are always at home, bringing up the kids. Every morning we're preparing breakfast for them, there's pandemonium in the kitchen, alarms going off, who has a rugby match, who has a football match. We cook for them; I know it sounds crazy! They love beans on toast; it's Heinz but they think it's my recipe. One of them said, 'Don't give your recipe away, Mummy,' though my youngest won't touch them; he thinks they're absolutely disgusting."

Like many mothers who've served their time during the children's early years, Bertarelli's now having her moment. "They're old enough I can do a little touring and promotion and not have it affect them. It's good for your children to see you working and having goals and aspirations."

Still, there are child-care hassles. "Ernesto's in London doing business so we had to think about it. Chiara can board a couple of nights, my second is on a school trip, the third one was a problem but then we realised he could stay with his cousins. Sorted!"

Having sung at charity fund-raisers, four years ago Bertarelli signed a deal with the Swiss branch of Universal Music. "My album went into the top 20 and I have my little fan base there," she says. Then last year, Ernesto helped fund her second album, Love Is, featuring her duet with Ronan -Keating. Several tracks were mixed by techno and dance DJs; one, Hands High, was championed by Radio One's Dance Anthems.

Vanity recording is the Ming china elephant in the room. Her husband isn't bankrolling this album, she says; she has her own deal with Decca. "I don't think Ernesto is going to stop working and rely on my income just yet. It still feels fantastic, though. It's important to make your own money - it makes buying a present mean so much more, and it's important for your own self-worth, self-belief."

So what of Indigo Shores? Well, Bertarelli's voice is fine - no worse than Madonna's, put it that way. It lacks the emotional whoomph of Adele, one cited influence, but it's pleasant Magic FM fodder. My children enjoyed it. "Which songs did they like?" Bertarelli inquires sharply, suspicious of insincere compliments.

The songs give more insight into the Bertarellis' life than she's prepared to communicate in person. Several are influenced by holidays in Indonesia, the US, riding on Ernesto's Harley, about him proposing to her in Mexico to the strains of a Mariachi band. There's one about her daughter turning 13 ("It's tough as a mother, you have to stand back but at the same time you have to be there"), another about her "magnetic" love for her son - inspired by watching waves in the moonlight, waiting for Ernesto to return from sailing.

Disappeared, the first single, is about "how we want to be accepted for ourselves, to be loved faults and all. Like if you're messy." Is she messy? "Yah, Ernesto can't understand why I can't cut bread neatly. But it's hard, right?"

It's not going to be easy to persuade the public to love Britain's richest woman for what she is, but I commend Bertarelli for trying. "I'm so nervous when I sing in public," she says. "Everything in my body is shouting, 'Don't do it! But you have to overcome terror; you'll never know what could have been if you don't take risks."

The Telegraph, London