“There’s no way this will flop,” says Christina Domecq, founder of Spinvox, a voicemail-to-text telephone service that launched on Friday. “It’s a simple solution and simple solutions don’t flop. And I’ve got an amazing team behind me.”

Domecq, the American- educated scion of the Spanish sherry family and, at 27, already a computer-service veteran, thought up her business idea in a eureka moment outside Seville two years ago. Sitting in a car after a meeting, listening to 14 voicemails on her mobile and desperately scribbling down the numbers to ring back, she thought: isn’t there some way this could just be converted to text and sent to me? She asked a friend. There wasn’t. The big network operators didn’t think it worthwhile. So she reasoned that if she could invent a service that did just that, turning voicemail messages into text and sending them on, she might have found a very profitable niche.

And then — unlike the rest of us, who would have filed the idea away and got on with something more mundane — she spent the next 18 months pulling together the technology for Spinvox. Now here she is, rolling it out in Britain. It’s the first of a clutch of phone add-on services the company plans to launch, and it could make her very successful indeed.

Or, of course, it could flop, but Domecq doesn’t allow that possibility. Sitting in swish rented office accommodation off London’s Piccadilly Circus, dressed in an austere dark trouser suit and sharply pointed shoes, she runs through the research and partnerships that, she says, ensure her new venture will be successful.

Her assurance — bred, no doubt, from reading philosphy and economics at Boston College and finance at America’s prestigious Notre Dame University — is rather frightening.

“We are about servicing busy people,” she says, in her tight, American East Coast accent. “If you look at the history of voicemail, it hasn’t really changed in the last 15 years.”

She knows there is the demand for something different and has already done the rounds of the big corporations and researched consumer needs. She’s doing deals with retailers and air-time resellers. It cannot fail.

But hang on, if the idea’s so smart and so simple, surely big network operators would be doing it themselves? “No,” she says, “they’re focused on 3G at the moment, and their creative teams are not based in the here and now. We want to focus on the here and now.”

Domecq evinces a stolid seriousness way beyond her youthful appearance. She has already, in her short working life, launched, grown and folded a computer-training franchise with a $12m (¤9.7m) turnover in New York, and helped reorganise a ship-brokerage business.

You’d guess she had to grow up fast. Her parents divorced when she was young and her father, Michael Domecq, who set up Domecq’s American drinks business, was later indicted for fraud and tax evasion, and now lives beyond the reach of American justice in Spain. Her American mother died of cancer 11 years ago, leaving a teenage Domecq, the eldest of six children, as family head. All that would give anyone a serious side.

Anyway, figures first. The Spinvox service costs about £10-£15 a month for the average contract holder taking five voicemails a day. It works for all users, provided their network supports call diverts. Domecq, with a team of 15 and private equity backing, is confident she will have 100,000 regular subscribers by the end of the first quarter of 2005, and maybe as many as 250,000 when the firm is a year old.

Then Spinvox is likely to target America (easier than adapting the software for different languages in Europe).

Those who have tried the service say it’s great, but you have to get an irritating amount of voicemails to make it worthwhile. For business users, however, it should be an easy sell.

That’s not to say that big network operators are falling over themselves to welcome her launch. They’ll benefit from the extra texting revenues, but ask them about voicemail to text and they’ll tell you they don’t believe the software exists to turn all speech into flawless text, regardless of accent, reception and so on. Nor are they convinced there is a huge demand for the Spinvox service — it’s like paying extra to be paged.

And in the scheme of what’s going on in the content and service sector, which is anticipating a dotcom-style boom with 3G, Domecq’s start-up is just another niche to them.

Domecq cut her teeth running her own computer-training start-up in New York five years ago before the dotcom crash and September 11 kicked a hole in the business.

Even then, those who saw her were struck by her maturity. “She had guys in their forties reporting to her,” says Spinvox co-founder Daniel Doulton, “and they felt comfortable following her lead. She makes decisions, and she makes things happen.”

Doulton, 35, a former Psion executive, first met Domecq on holiday in the Alps. He was running a paragliding company after losing faith in big business. Doulton trained in electronics engineering but with stints at consultant Arthur D Little and Citibank under his belt, was the first person she turned to with the Spinvox idea. He had the contacts and know-how to turn her vision into reality.

So today Domecq will be at Portsmouth harbour, waving off the yachts in the Global Challenge race. Spinvox is co-sponsor of the Save The Children boat — yachting, like rock climbing, scuba diving and paragliding, is one of her passions.

Isn’t launching a start-up enough? She laughs. “You’re right, I don’t have any leisure time now anyway,” she says. And if Spinvox flops? “Simple solutions don’t flop!” she reminds me firmly. Ah yes, I’d forgotten.