The saying goes that this race is never won in a single day but it can be lost on any day. Yesterday the truth of this came back to haunt the French national champion, Christophe Moreau, as his chance of victory evaporated in the Camargue heat as a consequence of the bike-racing equivalent of the horseshoe nail that lost the war.

Cut and bruised after an early crash and exhausted after 40 miles of desperate pursuit, Moreau crossed the finish line here three minutes and 20 seconds behind the day's winner, Robert Hunter, the first South African to take a stage victory on the race, and slipped from sixth overall to 12th, more than six minutes behind the leader, Michael Rasmussen.

The crash was not, directly at least, the cause of Moreau's woes, although the fact he damaged one of the cleats that fix his shoes to the pedal was critical.

The Frenchman then fell victim to a tactical move known in French cycling slang as un coup de bordure - or "stab in the gutter" - which has to do with the formation cyclists adopt when the wind is blowing strongly from one side.

As the field approached the feeding station on an exposed stretch of road on the marshlands south of Nimes, Alexandr Vinokourov sensed the wind blowing off the Mediterranean and told his Astana team to raise the pace at the front of the peloton.

It was an opportunistic move from the Kazakh, who may have lost most of the skin on his knees and buttocks but has clearly retained his racing instincts.

In a sidewind, riders scrabble for shelter and end up in a line, called an echelon, or fan, that stretches diagonally across the road from the windward side.

The number of riders in the echelon depends on the width of the road, and those who cannot find a place in the diagonal line end up in a line in the leeward gutter.

The wind blowing from the side means the line in the gutter will stretch and snap as riders find they cannot maintain the speed of those in the fan. When that happens, those who are not close to the front have no chance of regaining contact with the leaders because of the length of the line.

The "gutter stab" is a textbook move that is tried at least once in every Tour, but no one can remember the last time it actually worked.

There is much talk about cycling being in the gutter these days; yesterday the gutter was very much the place to be.

Moreau was at the back of the field changing his shoes when the echelon formed. A gap opened in front of him and by the time he had marshalled his team-mates to form a second echelon, the damage was done.

Another big loser was David Millar, on the rebound after a couple of days contending with a heat rash. The Scot bridged a sizeable gap to what appeared to be the five-man stage-winning escape, only to find that, behind, Vinokourov had ordered his troops into action.

"Astana wrecked my plans," said Millar. "It took years off my life getting across to that break, and getting caught was a big disappointment."

His morale is on the up but the rash makes his arms and legs seem as if they have been microwaved.

Moreau, on the other hand, now looks merely half-baked.

Guardian Service