Formula One Brazilian Grand Prix: The grand prix circus arrived in Brazil this week with Bernie Ecclestone making no pretence about his desire for Lewis Hamilton to win the world championship and become an ambassador for the sport as it expands into the vast new markets of China and India.

Formula One's ringmaster may be 76 but he has daughters of Hamilton's age and he can see very clearly how the 22-year-old projects an identification with the modern world to a greater extent than either of his rivals for the title this weekend.

No one knows better than Ecclestone that the drivers remain Formula One's most effective salesmen. And, despite the sport's eternal devotion to technology, they are also the ultimate component of the racing package. As the 2007 title race reaches its climax in Brazil tomorrow afternoon, the outcome of a uniquely turbulent season rests on the coolness and judgment of three very different personalities, each of whom is about to be subjected to the fiercest examination under pressure.

Even within a sport dependent on a level of technology now far beyond the comprehension of a non-specialist, the human rivalry remains paramount. So tomorrow's race is less a contest between McLaren-Mercedes and Ferrari, whose cars are so closely matched that each team has won eight of this season's 16 races to date, than one between three drivers whose characters, given the similarity of their ages and ambitions, could hardly form a greater contrast.

This is the ninth three-way shootout in Formula One's history. The first, in 1950, took place between three drivers - Giuseppe Farina, Luigi Fagioli and Juan Manuel Fangio - who shared a Latin heritage and whose average age was 45.

This year's trio - Hamilton, Fernando Alonso and Kimi Raikkonen - have an average age of 25 and ethnic backgrounds ranging from the Caribbean to the Mediterranean via the Arctic circle. They represent the proof of the way a sport which was once an exclusive preserve has broadened its demographic base in a way that would delight any marketing department.

After a season defaced by rows and scandals, the present trio are approaching the climax of an epic struggle in which the result has been increasingly unpredictable.

Hamilton has become a household name in record time, his progress lubricated by a quick smile, a bright mind and a ready eloquence. He radiates energy and optimism. He is polite, thoughtful and gracious. Although he enjoys the trappings of his new fame, he was genuinely shocked when newspapers and magazines published paparazzi photographs of his holiday adventures. He has close relationships with his father, Anthony, who has guided his career with great vision, and his 15-year-old brother, Nick, whose cerebral palsy has forced him to use a wheelchair.

Alonso, after becoming the youngest champion in the history of the sport two years ago, seemed to be the leader of a new, post-Schumacher generation of drivers. He was charming and serious and popular with his mechanics in the Renault team, he kept his private life to himself, and he showed an engaging lighter side in his fondness for magic tricks. There were times, however, when frustration got the better of him.

This season, since he discovered that Hamilton was at least his equal in the cockpit of a McLaren, there have been further sulks and bursts of anger.

Raikkonen is the oldest of the three and his only marketable asset is the sheer speed that has long given him the potential to become Finland's third world champion. The three drivers were asked whether they had memorised the complicated points-scoring permutations that would enable each of them to win the title. There was much to be learnt from the way they gave their answers.

"Yes," said Alonso, a serious expression on his face as he contemplated the possibility of a third title. "Yes," said Hamilton, with a broad smile that spoke of an unspoilt enthusiasm. "I don't think about it so much," Raikkonen muttered. Any of them would be a worthy champion. Only a victory for Hamilton, however, would feel like the start of a new era.

• Guardian Service