An all-out attack by Alberto Contador on the race's first Alpine summit finish in Verbier saw the Spaniard seize both the stage and the overall lead yesterday, while a blistering performance by Bradley Wiggins propelled the Londoner into third place overall.
Lance Armstrong climbed to second in the general classification, but despite this improvement, yesterday will go down as the first time in a decade when the American all but admitted overall defeat in a Tour de France.
Crucially, the Texan was unable to follow Contador when the Spaniard - Armstrong's Astana team- mate, but also his arch-rival in this year's race - charged away 5.5km from the line.
In years gone by, the American would have had no problems crushing that sort of attack and probably followed it up with a knock-out move himself. This time, though, Armstrong flailed. Then he wheeled to one side of the road, as if inviting his rivals to give chase. They finally did so, but in the meantime, Contador was steadily soaring towards the summit n and the yellow jersey.
The Texan finally finished ninth, 1min 35sec down on Contador, and his look of sheer pain as he crossed the line indicated just how deep he had had to dig to stay in some sort of contention.
To describe this moment as historic is no exaggeration. After seven straight Tour wins and a comeback that followed three years in retirement, this was the first time since 1999 that Armstrong had failed to dominate the race in the mountains.
Even in 2003, the one year where the American was against the ropes for most of the Tour, Armstrong had stubbornly stayed in the lead. But yesterday it was a Spaniard, who was just nine when Armstrong turned professional in 1992, who donned the yellow jersey.
"The best rider won today," Armstrong said, "and I was a little bit on the limit." Asked if he would now settle for second in Paris, the Texan laughed and said, "not before, but now I would!"
Contador, on the other hand, looked positively relieved as he delivered his trademark victory salute of an imaginary pistol shot when he reached the line, then raised his arms in the air.
His advantage over closest pursuer Andy Schleck of Luxembourg was just 43sec, but the Spaniard admitted his solo win had felt like "a liberation".
"I've been waiting for this stage for a long time, and it's worked out like I hoped it would. Last night I dreamed that I wouldn't have good legs, but finally I could attack even a little bit before I thought was possible."
Asked if he was happy to have beaten Armstrong, Contador sidestepped the question, simply saying, "I'm very happy to have beaten everybody."
Contador's knock-out move came at the end of a comparatively straightforward run starting in Pontarlier in France, edging round the side of the Jura mountains, to the day's one big challenge n the ascent to the ski station of Verbier in Switzerland.
The bunch's speed on the approach roads to the final 9km climb would have done credit to a bunch sprint but, after two weeks of stalemate, rather than the fastmen it was time for the overall contenders to come to the fore.
Wiggins' Garmin-Slipstream team, led by British team-mate David Millar, set the pace at the foot of the climb, shattering the bunch. Then when Astana's Andreas Klden moved ahead, the group instantly shrank to just eight riders, with Contador, Wiggins and Armstrong among them.
Once Contador had shot away with Schleck in hot pursuit, Klden and Armstrong tried to limit the gap, but Contador remorselessly stretched open his advantage.
Instead, it fell to Wiggins to try to keep the chasers in contention, and even attempt to break away alone at one point. His counter-attack fizzled out, but he received a huge morale boost when he was able to leave Armstrong behind to finish fifth.
Following today's rest-day, the race tackles the two hardest Alpine stages, and Wiggins' third place overall gives him high hopes.
"I trained hard mentally and physically for this but I'm not going to think too far ahead. In any case, this is fantastic."
Punching so consistently above his weight on the climbs makes this a breakthrough year for Wiggins, but it was overshadowed yesterday by Armstrong finally ceding ground to Contador and the next generation of Tour riders.
After the Pyrenees, the American had triumphantly claimed the Tour had come down to a straight fight between himself and Contador.
But if that was the case, as Armstrong confirmed he would work for the Spaniard in the remainder of the race, yesterday the Tour all but became a one-man show.
- THE INDEPENDENTBy Alasdair Fotheringham