By Matt Slater BBC Sport

Landis was broken and beaten after stage 16; his recovery won the race

Cycling is hurtling down the side of a mountain, without any brakes, towards becoming as palatable a sport as bull fighting and body building.

To say the discovery that the winner of the Tour de France may have been cheating is bad news is perhaps the biggest understatement since James Lovell told Mission Control, "Houston, we've had a problem."

Of course, Floyd Landis may be cleared, but with its credibility already hanging by a thread, the Tour needed this like a stick in the spokes.

The hardcore fan won't mind - there is almost as much masochism involved in following a minority sport as there is in actually riding the Tour.

They've been here before (Tom Simpson in 1967, Pedro Delgado in 1988, the "Tour of Shame" in 1998 and far too many others to list here) and some take a remarkably laissez-faire attitude to their heroes' refuelling habits.

But the part-time enthusiast - the fan who finds as much joy in watching Riquelme run a game, Lara compile a ton or Tiger plot his way around a course - will be, in order, shocked, not shocked, disappointed, mildly amused and then resolved not to care about the Tour so much next year.

Belgians and lycra-clad diehards, like the chap who runs alongside the riders dressed as a devil (how cycling could do with an angel running along on the other side) will be back. But who else?

You build up a new hero and he gets slapped down - it's very serious Dick Pound World Anti-Doping Agency

Already this year's race - the first after Lance Armstrong's seven-year hegemony and the most dramatic for years - was watched by fewer people, at the roadside and at home, than previous years.

Even the French, whose riders actually had a decent race for the first time in a while, seemed to be fed up with watching La Grande Boucle suffer a death by a thousand cuts.

Phonak, the hearing-aid company that bankrolls Landis' team, has had enough.

The message that cycling isn't quite as wholesome as it ought to be has got through loud and clear - the 30-year-old Landis is the fifth Phonak rider in two years to have failed a drugs test (albeit in Landis' case just half a drugs test at this stage).

And German television station ZDF didn't waste any time before putting the boot in.

"We signed a broadcasting contract for a sporting event, not a show demonstrating the performances of the pharmaceutical industry," said ZDF editor-in-chief Nikolaus Brender.

Landis' team have had more than their fair share of doping problems

Catty, but when you've just seen the man you were pinning your coverage on, Germany's Jan Ullrich, apparently uncovered as a drug-taking phoney you're probably entitled to a bit of moral indignation.

The real point of the Landis affair is not that he may have applied a testosterone patch to his scrotum for a few hours to help recover from a bad day in the Alps, it is that cycling and drugs have become synonymous.

What was once a drip-drip leaking of cycling's integrity has become a torrent. A look back at our cycling page over the last 12 months makes very depressing reading - race report, doping story, race report, doping story and so on and so on.

World Anti-Doping Agency boss Dick Pound said cycling's image was "in the toilet" after 13 riders, including the two favourites, had been kicked out for drug allegations before the Tour started.

It must be somewhere very dark and smelly now.

"When is this going to end? What is the UCI (international cycling's governing body) going to do about it?" asked Pound after news of Landis' positive A sample was revealed.

"You build up a new hero and he gets slapped down. It's very serious."

I don't think it's ever going to go away no matter what happens next Floyd Landis

Serious indeed, because if any sport needed its heroes right now, cycling is it, and Landis appeared to fit the bill perfectly.

After retirement and a Spanish investigation had combined to rob the Tour of last year's top-five finishers, the tale of a man who had battled against family pressure, bad luck and worse injuries to win cycling's showpiece - with one of the bravest rides in the 103-year history of the race - was a godsend.

It now looks like a cruel joke.

Landis has pledged to clear himself but he has not got off to the most convincing of starts.

"I don't know what the explanation for (the positive test) is, whether it was a mistake or whether it's an occurrence from some other circumstances that go on in the race or something I did," said Landis.

He then listed three (scientifically dubious) reasons why his testosterone levels might have been out of whack after his yellow-jersey winning efforts in stage 17.

A few beers? Cortisone shots for his dodgy hip? Pills for his thyroid problem?

Landis will lose his yellow jersey to Oscar Pereiro if the B test is positive

Realising that he was starting to sound like a husband with no flowers on anniversary day, he admitted: "I wouldn't hold it against somebody if they don't believe me.

"Unfortunately, I don't think it's ever going to go away no matter what happens next."

What happens next... that is, of course, the $64,000 question for Landis and cycling, as the short-term fates of both are now inextricably linked.

His team are adamant about his innocence and there are no shortage of character witnesses just looking for a branch to grab hold of so they can come out in support of their man.

Landis has also hired a medical expert who he says has a 100% record of explaining away elevated testosterone levels to the satisfaction of this matter's probable final judge and jury, the Swiss-based Court of Arbitration for Sport.

But that isn't going to happen any time soon.

In the meantime, Landis and cycling are being tried in the court of public opinion.