She speaks of hunting for technological "disrupters" and is paranoid about missing out in the hunt for entrepreneurs who have the next big thing. "Often, if they find you it's a bit late," says the 36-year-old.

Stenbeck is one of the most powerful business names in Sweden, heard in the same breath as the Wallenberg family or the Perssons behind fashion giant Hennes & Mauritz.

Yet Cristina Stenbeck was born in New York and speaks Swedish with an American accent, having learned the language of her father Jan only as a teenager.

She inherited Kinnevik at the age of just 24, not long after she had finished her studies at Washington's Georgetown University, on Jan's sudden death from a heart attack in 2002.

In little more than a decade, she has transformed the group into one of Europe's leading investors in e-commerce, including in the continent's biggest online fashion retailer, Zalando.

No stranger to fashion, her first job out of university was in Ralph Lauren's direct mail and marketing department.

"That comes in handy now," Stenbeck said at her office in London's Mayfair district, where she deals with issues such as improving product lines and promoting more lucrative private labels as the new supervisory board chairwoman at Zalando.

"I have always been interested in fashion," she told Reuters in a rare interview, wearing a navy blue dress, matching heels, her blonde hair tied up in a neat bun.

Kinnevik's London office lies between the Zaras of Regent Street and Chanels of New Bond Street, while a Ralph Lauren store is next door.

Father Jan had already turned Kinnevik, which began in 1936 and built up chocolate, iron and paper businesses, into a media and telecoms empire when Cristina became the third generation of Stenbecks to run the family firm.

The dotcom bubble that sent stocks in Internet companies soaring around the turn of the century had just burst.

At first some wrote her off because of her youth; others, burnt once by the dotcom mania, disagreed outright with her push into e-commerce. But she grew into her role, and those near her describe her as stable, smart, alert and ambitious.

OUTPACING THE WALLENBERGS

Jan Stenbeck was responsible for modernizing Kinnevik, turning it into the giant behind the Tele2 telecoms group and the free Metro newspapers.

He famously broke down the Swedish state broadcast monopoly in the 1980s by transmitting from London, giving Swedes their first TV commercials and clinching rights for the 1989 world championships in ice hockey, which is wildly popular in Sweden.

Jan had made it clear early on that Cristina, the oldest child in the family, would take the reins after him and she got her first board seat at only 19.

Today she is executive chairwoman of one of Europe's largest listed investment companies with a 75 billion crown ($11 billion) market capitalization. Kinnevik owns significant stakes in over 50 firms that span financial services, media, telecoms and online businesses in more than 80 countries.

Its share price has shot up over 1,000 percent since 2002 - more than twice the rise in the Wallenberg-backed Investor Group.

Unlike other family-run investment groups which tend to stick to what they know best, managing the same assets for decades, Kinnevik has no qualms about dumping old investments to fund new ventures and innovations. Industry makes up only one percent of its portfolio today.

Cristina, who lives in London with her British husband and three daughters, does not like to compare herself with her father but comes across as equally hungry for innovation.

It is under her leadership that Kinnevik has become the biggest investor in Zalando, a household name in parts of Europe which sells everything from stilettos to handbags and has been valued by some analysts at as much as $9 billion.

Stenbeck, who goes frequently to Stockholm where the rest of the Kinnevik team work, ranked 34th on The Sunday Times' list of wealthiest women in Britain this year with 376 million pounds.

That figure is likely to climb if Kinnevik earns handsome pay-offs from investments in both Zalando and Rocket Internet which set the fashion firm up. Both are said to be heading for multi-billion dollar stock market listings.

TECH SAVVY

Stenbeck's cool, measured tone could not be more unlike her father who was known for his loud, often abrasive style. But her voice quickens when she talks about unchartered business territories such as in Africa where Jan struggled to break into new telecoms markets.

"The fact that we are in Nigeria, and not limited to the fact that my father couldn't get a license there - I love that," she said. "These are new big-population markets."

Kinnevik has put increasing resources into Africa, backing Jumia - a would-be African Amazon in Nigeria which is also a Rocket Internet venture. Instead of celebrating the midsummer holiday in Sweden this month, she is in Africa hunting for new places to put her money.

She feels her tech savvy helps.

"I think there are lots of owners in their late 60s or 70s who have one proven approach. I think it's a real benefit for the Kinnevik investee companies to have someone who is flexible and immersed in the world of technology," she said.

"I think if we sold chocolate or paper and pulp packaging products a different style might be required. I think my style is pretty well-suited."

Stenbeck wants to build digital brands globally for decades to come and she hints she may have already found the next investment, in digital financial services.

"All of these investment decisions are milestones on a journey that for me I see is a 30-40 year horizon," she said. "That's literally my lifetime to date."

She has worked hard to create her own legacy and is looking ahead to the next generational change. "To hand over a collection of powerful brands to the next generation – the fourth generation – is a very compelling proposition," she said.

($1 = 6.6883 Swedish Kronas)

(Additional reporting by Emma Thomasson in Berlin and Kate Holton in London, Editing by Alistair Scrutton and David Stamp)

By Mia Shanley

Stocks treated in this article : ASOS plc, Investment Kinnevik AB, Tele2 AB