Twelve months ago the memories were precious and the anticipation intense. The Tour, the biggest, best, annual sporting event in the world was here and the excitement hung in the Dublin air like the Coca-Cola bunting of the official sponsor.

Brightly-painted team cars purred through the traffic; walkways and podiums and giant television screens transformed the streets. And from the moment when Denis Leproux of the Big Mat Auber team hurtled down the starting ramp of the prologue time trail, 950 million homes worldwide tuned into an Ireland which had welcomed the event with outstretched arms.

A year on, you can practically taste the difference. The travelling circus that is the Tour has moved on, the festivities continue but beneath the colour and the noise there is something different about the whole thing. An underlying sadness, a pain behind the smiles. That euphoric party has become little more than a wake.

Later this afternoon in the French theme park of Le Puy du Fou, 189 riders will once again roll down the starting ramp. But this time each one is launching himself into something far more than just a prologue time trial. One year ago a succession of doping scandals and drug seizures revealed the dark heart of the Tour de France in particular, and sport in general. It was a slash across the underbelly of cycling, and the guts of a great, untold secret spilled out onto the roadside.

This year's Tour, already dubbed the Tour of Redemption because of greater medical testing, a new charter of ethics and an effort by the race organisers to ban undesirable individuals before the competition even begins, will show if the injured beast can recover, or if its condition has become terminal.

"We thought doping was the problem of one team," said Jean Claude Killy, President of the Societ e du Tour de France at the launch of the 1999 Tour last November, "but we quickly understood that it was a problem of the sport as a whole. Everybody knew it, but nobody admitted it. The Tour lives on but it will never again be a symbol of doping, but instead a symbol of the fight against doping."

Strong words, bravely spoken. And one certainly hopes that Killy is correct, because the patience of sponsors, the media and the general public has been stretched to breaking point. On the eve of the start of the race, one of the biggest sponsors, Credit Lyonnais, has already suggested that it it growing weary of the controversies enveloping the race. Any more scandals, any more rider's strikes, any more drug busts will surely see the unbuckling of Le Grande Boucle. One bitter pill too many.

There was a moment in last year's race which reflected the changing mood in France. When team soigneur Willy Voet elected to nonchalantly cruise across the Franco-Belgian border with a car boot full of performance-enhancing drugs and thus implicate the whole Festina squad, the over-riding reaction was initially one of indignation. Richard Virenque, second in the previous year's race and the darling of France, was one of those fingered by Voet's confession, and when he was eventually thrown off the race, many of the roadside supporters fumed. "Virenque kicked out . . . a scandal" said one banner of support,

"Festina eliminated - but what of the other 20 drugged teams?" shouted another.

It epitomised the hushed comprehension of a culture which had gone hand-in-hand with the sport for decades. "You don't ride the Tour de France on mineral water" said five-time winner Eddy Mercx years ago, and it is a sentiment with which many supporters privately agreed. The general attitude was that it was necessary to take something just to survive in the world's toughest sporting event. But as scandal after scandal unfolded in last year's race, some began to grow tired of the whole thing.

One year on, beleaguered race director Jean Marie Leblanc must win over a cynical public. For the past 12 months he has striven to convince the riders, team officials and directeurs sportifs who for years have accepted the culture of the needle that there is another way. Has tried in 12 short months to turn around what came about after decades of hushed whispers and averted gazes. Has tried to woo the French press who spill out the questions which they neglected to ask for so long.

And all this, it seems, without the help of the head of the International Cycling Union (UCI) Hein Verbruggen. Having denied the existence of systematic drug abuse for years - despite the testimonies provided by former professionals such as Giles Delion, Paul Kimmage, Nicolas Aubiers, Erwann Mentheor and Graeme Obree, and a succession of deaths linked to the use of EPO - Verbruggen remained on holidays in India last July while the Tour controversy blew up into a storm. Many feel he never really came back from his holiday. For since then he has blocked a mandatory two-year ban for serious doping offences at the Irish Olympic Committee congress in Lausanne, told Italian professionals that they weren't actually obliged to succumb to the extensive medical testing imposed by the Italian Olympic Committee in May's Tour of Italy and, most recently, forced Tour de France organisers to readmit Richard Virenque and Once team manager Manolo Saiz into this year's race.

The last intervention, in particular, has infuriated Leblanc, who had banned the two for fear of further recriminations during the Tour. "The Tour de France Organisation deplores the position that the UCI has taken under the pretext of a technical breach of UCI rules, but comes at a cost of the defence of fundamental sporting values," stated a press release earlier this week.

While there are reasons to believe that French cyclists have started to clean up their act, the phrase "cyclisme a deux vitesses" (cycling at two different speeds) has been oft mentioned - French cyclists have been left floundering in the wake of cyclists from other countries, yet the average speed of races has been going up. A rejection of the old ways by the international peloton? It would seem not.

This slow pace of reform comes at a time when the international press is salivating at the thought of further scandals - and Judge Patrick Keil is set to release his 5,000-page report on the Festina affair during the middle of the Tour. Clearly, despite his best efforts, Leblanc is rapidly running out of gears.

If there is a modicum of consolation for the sport of cycling, it is that last year's revelations have meant that it has at least recognised the existence of a problem.

Despite growing evidence, the testimony of a number of participants and the simple weight of logic, international federations of other sports still maintain an air of purity and a steadfast insistence that drug use is isolated. But the disconcerting rumblings seen in cycling five years ago are starting to appear across the board.

Allegations of EPO abuse in marathon running, steroid abuse in rugby - even the beloved French World Cup soccer squad have been drawn into the fray. Emmanuel Petit recently warned of growing drug abuse in professional football, and earlier this week his World Cup team-mate Christophe Dugarry tested positive for the steroid nandrolone.

"Why should cycling be any different?" asks former Tour de France winner Stephen Roche. "The same money, the same pressures are there in every sport. The one good thing for cycling in all of this is that after last year's Tour we have started to try to address the problem. And in five or 10 years time, chances are that we will be the sport that others will hold up as an example as to what can be done."

But the pressing question is this one: Will the Tour de France survive long enough to prove him right?