LONDON - Cycling is undergoing a revolution and Saturday's Tour de France start in London is the perfect symbol of the changes the sport is going though, race director Christian Prudhomme believes.

"Things are changing a lot even though the public does not really realise it," Prudhomme told Reuters in an interview.

"The world of cycling is really going through a revolution. There is wrestling between those who dream of a different sport and those who cannot quit their old habits."

Prudhomme, who is taking over from the departing Jean-Marie Leblanc as Tour director, said more efforts were being made in the fight against doping.

"These last 10 weeks, 160 random tests were conducted while there were only 150 in 2006. We are waiting for the results and hope they will be known before the start of the Tour," he said.

The riders have been asked to sign the UCI's anti-doping charter, a document that asks riders to pledge a year's salary in the event that they test positive for a banned substance in the future.

The letter, which begins with a declaration that the rider has not been involved in any past doping affair, will be sent for signing by July 7.

Prudhomme has made clear that any rider who fails to sign the charter by then will not be allowed to start the Tour.

"What is absolutely necessary is that the riders show a will to commit themselves. They have to show their will," said Prudhomme.

The race will start in the English capital with a 7.9-km prologue.

"Starting from London is a huge chance that is given to us," said Prudhomme.

"For a sport that is seen as naff, it is quite something to be here in London, the place to be in 2007. London is opening its heart, its monuments to us, it's absolutely fabulous."