The internet poses a complex challenge to the world's biggest mobile phone company, chief executive Olli Pekka Kallasvuo tells David Ibison.

Olli Pekka Kallasvuo, chief executive of Nokia, one of the world's biggest and most influential technology companies, is not a $6,000-shower-curtain kind of guy. Stocky, wearing a dark suit and indistinct tie, it is impossible to imagine him succumbing to the boardroom excesses that other companies have struggled with in recent years.

"Success only is not a good thing in business," he says. "It makes you very humble when you have seen things go bad."

This practicality was emphasised when he was appointed chief executive earlier this year. There was a sort of collective exhalation that seemed to mark the end of an era.

To say Kallasvuo, a former chief financial officer, was the world's most dynamic public speaker would be a stretch.

Investors and analysts braced themselves for a period of laconic leadership after the charm and panache that made his predecessor, Jarno Ollila, Nokia's poster boy during the technology boom. But consider the company Kallasvuo leads. The Nokia story is one of a company dumping businesses linked to its historical roots making rubber products such as galoshes, to concentrate on telecommunications.

It has had to weather enormous feuds between its two controlling shareholders, Union Bank of Finland and Kansallis-Osake-Pankki, that almost led to its being taken over by arch rival Ericsson of Sweden.

It had to overcome the collapse of Russia, its big market at the time, a Finnish recession, a disastrous foray into television manufacturing, the mysterious suicide of Kari Kairamo, its chief executive, and boardroom infighting.

Then came the 1990s boom, the deregulation of the market for telecommunications across Europe and the introduction of the GSM common standard for mobile telecommunications. Mixed with the successes were two consecutive profit warnings in the mid-1990s and a collapse in sales in 2004 after it failed to spot the trend towards clam-shell phones.

Nokia's background is one of change, reinvention, opportunism, technical expertise and occasional disaster. It has had more comebacks than Elvis .

After entering a modest meeting room at Nokia's pristine but somewhat sparse glass, steel and pale-wood headquarters near Helsinki, Kallasvuo reaches for a glass of water, having been worked hard by his tennis coach that morning.

He prefers not to talk about Nokia's past but it is hard to believe that, given Nokia's incredible history and his 25 years at the company, he somehow eschewed all the drama.

A more credible explanation is that while Ollila was on magazine covers, Kallasvuo was the crucial member of the team that created the Nokia of today.

One anecdote illustrates this. In 1993 Kallasvuo had an important role in deciding to strip out Nokia's results from its individual business units. This made plain that its mobile phone business was growing rapidly but being dragged down by the group's other operations.

One fund manager, Laurence Solomon, met Kallasvuo, looked at the numbers, declared them to be "the biggest thing ever" and bought all the Nokia stock he could lay his hands on. It was a seminal moment. He and others made a fortune as its shares rose from €3 to €62 by the late 1990s.

"He made some money," says Mr Kallasvuo coolly, pointedly refusing to take any credit for the development.

It is this discreet but powerful influence that helps to explain why Kallasvuo was chosen to lead Nokia into what promises to be a period of change worthy of its dramatic past. Mobile phone technology is converging with the internet and Nokia will have to evolve to retain its leading position.

"There is only one internet," Mr Kallasvuo says. "Nokia is going to be an internet company. It is definitely a mobility company and it is making good progress in becoming an internet company as well."

This is a fundamental change. Whereas once its competitors were Motorola and Ericsson, it is now in competition with Apple Computer, Yahoo, Google, Microsoft and Canon, plus a host of unknowable but advanced small-tech companies beavering away in laboratories to develop the next big thing.

This is how Pekka Ala-Pietila, a Nokia board member, summarised the situation: "Five to 10 years ago you would set your vision and strategy and then start following it. That does not work any more. Now you have to be alert every day, week and month to renew your strategy."

Kallasvuo concurs. "The world is more uncertain and in that way it is more complex and that environment will almost by definition mean that you have to take more choice and in that take more risk than has been the case in the past. It is the complexity and speed of the internet."

The challenge for Kallasvuo is going to be preparing Nokia, which has nearly 60,000 employees, to spin on a dime if need be.

"You need to have years of economies of scale and you need to have flexibility and responsiveness, and then find the right balance between the two," he says.

"We need to be more pro-active in the areas of technology and functionality, in coming early to the market - emphasising time to market as opposed only to economies of scale."

Kallasvuo is somewhat dry, but whereas it used to be essential for chief executives to cut a dash in public, those days have given way to a more sophisticated age that can tolerate the return of the businessman or woman. And Mr Kallasvuo is a businessman.

"Leadership, all in all, is really the ability, willingness and even guts to make decisions. When you make decisions and you see them fail, you have to accept that and be mentally strong."

He admits the internet poses one of the most complex challenges Nokia has faced, but he gets surprisingly animated talking about it.

"There is no future in defending," he says. "Staying put is not a possibility."