I live in Paris, and the Tour de France starts on Saturday, but you’d barely notice it. You don’t see posters of great cyclists in cafés, I haven’t heard a single conversation about the race, and the French sports newspaper L’Equipe – whose ancestor L’Auto invented the Tour – has been putting football on its front page. The figures show that doping is finally destroying the legendary race. The people who still watch it now watch with irony.

Once cyclists were European heroes. Long-dead racers such as Fausto Coppi and Jacques Anquetil remain more famous than anyone starting in Monaco on Saturday except the 37-year-old Lance Armstrong.

It’s not that the dead men were clean and the current ones cheats. Doping has always been part of the Tour. It was long accepted, even embraced. The race never aspired to Olympian purity. It is all of life, good and bad, and it’s also a French odyssey, complete with the wines of each region and pretty girls and other French delights.

The Tour declined when tolerance for doping did. In 1998 police caught the Belgian sports physiotherapist Willy Voet with a car full of drugs. (Voet had taken a pot belge – cycling slang for a cocktail that can contain cocaine, heroin and amphetamines – just to stay awake on the drive.) The extent of the doping shocked fans, especially newer audiences such as Germans and Americans who were less blasé than the French.

Scandals became part of Tour tradition. Yet audience figures held up for a while. I asked a friend, a cycling nut, why he still watched cheats. “Even with dope,” he explained, “you’ve still got to go up the Mont Ventoux.”

Eventually the scandals became too persistent. People began to switch off. Kevin Alavy at Futures Sport and Entertainment, a research consultancy, says the average television audience in a number of important markets has more than halved since 1998. The Tour’s final stage drew a global audience of 22m in 2003 but only 14m last year. Many sports events have lost viewers, but the Tour more than most.

In Germany, the two main television channels continue to show the race chiefly because their contracts make them do so. This year they will broadcast only 60 to 80 minutes a day – a quarter of that of previous years – and they intend to highlight doping scandals. In the US just a couple of hundred thousand people now watch a typical Tour stage. In Spain audiences have almost halved since 2000 despite Spaniards winning the last three Tours. Even the French are switching off.

Ominously, says Alavy, “The Tour has a particularly old audience profile.” It’s disproportionately watched by old men with Michelin guides of France on their laps and memories of Coppi in their heads.

The Tour’s organisers prefer to talk about the new markets they are reaching. Television channels in countless countries – even Fiji – are screening this year’s event. However, many of them are tiny outfits such as ITV 4 in Britain. Of the 1.3bn Chinese, for instance, fewer than 1m will watch a typical Tour stage. Even globalisation cannot help this race.

Having said all that, the Tour remains massive. The only annual sporting events that draw more European viewers are football’s Champions League and Formula One. The Tour still beats Wimbledon.

But crucially, people no longer watch like they used to. They gaped in awe at Coppi and Anquetil. Now they watch with ironic distance, says Albrecht Sonntag, sociologist at the Ecole Supérieure des Sciences Commerciales in Angers, France. Ironic distance is a trend among spectators of most sports, but the Tour probably leads the pack here. At one recent stage, three young women lined the roadside with the letters “E”, “P”, and “O” painted on their bare bellies. To make sure the riders noticed their reference to the popular drug, they exposed more tantalising body-parts. Some riders were delighted. At least the women were there. In another decade they may no longer bother.