Cavendish emerged to the left of veteran sprinter Robbie McEwen to become only the second British rider to win back-to-back stages in a Grand Tour with victory in stage 13 from Narbonne to Nimes.
The quick run-in to Nimes was perfect for the sprinters, but the old guard of Erik Zabel, Thor Hushovd and McEwen once again had no answer to Cavendish’s speed in the final 100 metres.
“I was trying that hard, so to get another win was really good,” said the 23-year-old.
“It’s impossible to comprehend but now I’d see it as a failure to not carry on winning.
“The sport has always appealed to me – I’ve always loved it. I like my motor bikes, being from the Isle of Man. “But the fact cycling is down to the rider, not the engine, appeals to me a lot.
“I only planned to do 10 days of the Giro de Paris but finished it, and now I’m 13 days into the Tour not feeling too tired – I’ll take every day as it comes and see how far I can get.”
Australia’s Cadel Evans retained the race leader’s yellow jersey, one second ahead of Frank Schleck of Luxembourg. Cavendish’s powers of recovery are renowned, but even he was expected to struggle after the exertions of yesterday, where he won another bunch sprint into Narbonne.
Once again, Cavendish’s route seemed to be blocked, this time by Hushovd and Mark Renshaw of Credit Agricole.
Milram had also given Zabel an ideal benchmark entering the final kilometre, but Cavendish’s timing to pop out from behind Hushovd was again impeccable.
The 23-year-old is only the second sprinter in the last 10 years to win four stages in the same Tour de France, the other being Alessandro Petacchi in 2003.
It remains unclear if the Manxman will stay in the Tour through the Alps, in order to challenge for a fifth win on the Champs-Elysees, or whether he will be withdrawn to prepare for the Beijing Olympics.
Another win would draw him level with the five stages won by Lance Armstrong in 2004.
Cavendish praised the lead-out provided by his team, Columbia, but expressed disappointment that his four victories have not lifted him any closer to the green jersey.
“It was a real battle out there, but somehow I’m still no closer to the green jersey,” Cavendish added.
“I don’t know what I have to do! It just proves that you have to be ultra-consistent to win the points competition.
“I was tired, but ever since I was 13 I’ve shown that if there’s a win up for grabs, I forget everything and motor.
“Again the lead-out was perfect, the real hard work was done for me.
“The conditions were supposed to be kind, but when we reached Nimes there was a real block headwind.
“It didn’t feel like my most comfortable win.”
Oscar Freire, who finished fifth in the stage, holds onto the lead in the points competition by 28 points from Cavendish and Hushovd.
Gerolsteiner domestique Sven Krauss was fortunate to avoid a nasty accident when he collided with a road sign in with 10km to go.
The 25-year-old German’s bicycle was split in half by the impact, but Krauss’ injuries looked minimal and he rejoined on a new bike.
Midway through the stage, it emerged Riccardo Ricco had been sacked by Saunier Duval-Scott, along with team-mate and fellow Italian Leonardo Piepoli.
The disgraced Ricco, 24, returned a positive test for CERA, a third-generation version of the blood-booster EPO, for the Cholet time-trial.
Piepoli, 36, won the tricky mountain stage from Pau to Hautacam in a breakaway with another Saunier Duval rider, Juan Jose Cobo.
Piepoli was dismissed by the Spanish team for what team manager Mauro Gianetti called a “violation of the team’s ethics code.”