The Tour de France is one of the few great sporting events where close interaction between the fans and the stars is still possible, but in recent years the spectators have tended to let their enthusiasm get the better of them.

Predictions that some day a cyclist would be knocked off his bike in the mountains were realised here yesterday when the stage winner, Giuseppe Guerini, was brought down, fortunately with no ill effects.

L'Alpe d'Huez always attracts the lunatic fringe of fans - yesterday it was Danes in pink wigs - who every year, fired by over-enthusiasm and alcohol, flirt with disaster.

At the foot of the climb yesterday, for example, the French Bastille Day hero Stephane Heulot had to punch one enthusiast to stop him from yelling in his ear while he cycled up the mountain.

Guerini, a 29-year-old from Bergamo who finished third in last year's Giro d'Italia, had an opportunist win. He fell heavily, but got back on his bike assisted by the fan who had knocked him off in the first place while trying to take his photograph.

The race leader, Lance Armstrong, spent much of the climb to the finish fighting off attacks from the Swiss Alex Zulle, and the Spaniard Fernando Escartin, but without the same commanding presence as on Tuesday's mountain-top finish, and the leaders were caught unawares when Guerini made his move with two kilometres to go.

For the second day running, the Spaniard Abraham Olano suffered once the road started to climb, and he clung on to his second place overall by just five seconds as Zulle and his fellow Swiss Laurent Dufaux closed ominously. His inability to hold the pace yesterday enabled Armstrong to extend his lead to almost eight minutes.

The Texan was not troubled on the bike yesterday, but he lost his temper when a French television commentator asked him about the media reaction to his victory on Tuesday. The newspapers had made much of the American's uncanny speed.

"They can say what they like," said Armstrong dismissively. As if to strengthen the tense under-currents to this Tour, the testers from the Union Cycliste Internationale chose yesterday morning to carry out blood thickness tests on half the field. Armstrong's US Postal Service team was in the half of the field not tested.

The methods of getting round the tests, intended to restrict the use of the red blood cell booster erythropoietin (EPO), are now so well known that the consensus is that anyone who fails is either unlucky or arrogant; yesterday all the riders passed.

As so often happens, Bastille Day did not smile on the French, for all the television commentators' patriotic admiration at Heulot's outstanding courage.

The Breton, who wore the yellow jersey in 1996, stayed in front for almost 100 miles over the Col de la Croix de Fer, a 20-mile ascent to 6,300 feet above sea level. His brave effort looked ill-fated from the start, but it lasted until he was within sight of the chalets at the finish.

Richard Virenque retained his king of the mountains jersey but never looked strong enough to compete for the stage win.