Chris Froome cracked during a grueling climb to the finish and lost the overall lead in the Tour de France to Fabio Aru today after a demanding stage won by Romain Bardet.
Froome's Sky teammates had perfectly controlled the race until the final kilometer leading to the ski station of Peyragudes, but the three-time champion was dropped in a final section that featured slopes with a 20 percent gradient.
Bardet won Stage 12 ahead of Rigoberto Uran and Aru, who seized the race lead from Froome by six seconds. Bardet is third overall, 25 seconds off the pace.
Kiwi George Bennett moved up to ninth in the overall standings after another top 10 finish.
Team Sky had dominated the stage until the final 350 metres, when Aru made his move. Froome was only able to follow his Italian rival for a few meters before he cracked, and crossed the line in seventh place, 22 seconds behind Bardet.
Bidding to become the first Frenchman to win the Tour since Bernard Hinault in 1985, Bardet was the strongest in the brutal incline and described his third stage win on the Tour as "an immense joy."
He said he had visited the ski station with his parents to scout out the final climb.
"I knew it could suit me," he said. "I was patient. I made the difference on the final hill. There was not much to do before that with the wind and the Sky train."
Aru had trailed Froome by 18 seconds at the start of the stage.
"It's one of the most beautiful things that can happen to you in life, wearing the yellow jersey," said Aru, who rides for the Astana team. "Clearly, it won't be easy to defend it. There are still nine more stages, we'll do our best."
The final of the six ascents on the menu of the 214.5 kilometres (133 miles) stage between Pau and the ski station was too difficult for Froome, who had worn the yellow jersey over the previous seven stages.
He was grimacing with the effort, his arms glistening with sweat, as he wrestled his bike up the super-steep climb that was used a location for the 1997 James Bond movie "Tomorrow Never Dies."
Froome zig-zagged his bike across the tarmac as he tried to cope with a gradient so steep that it seemed to glue his wheels to the road.
"It was a very, very difficult finish," he said. "I did my utmost at the end. But I didn't have the legs to follow."
Rain was falling as the peloton started the stage in Pau, before a breakaway of 12 riders gained a lead of more than six minutes on some fairly flat sections of the course.
Froome's teammates rode at the front with Aru's squad just behind, but showed no interest in reducing the gap with the breakaways.
Sky stepped up the tempo in the first really difficult ascent, the Col de Mente, where Spanish great Luis Ocana crashed out in a downhill section in 1971 while wearing the yellow jersey.
The twisting and punishing Port de Bales, a narrow, 11.7-kilometre climb at an average gradient of 7.7 percent - rated as 'beyond a category' because of its difficulty - took a heavy toll on the lead riders. The breakaway group split up as Stephen Cummings launched a solo offensive.
Aru's teammate Jakob Fuglsang, who broke two bones in a crash during Wednesday's stage, struggled at the back and dropped out of contention after starting the day in fifth place overall.
Cummings had a two-minute lead at the top of Port de Bales and went all out in the descent as the fog broke and the weather picked up. Froome, Aru and Mikel Nieve misjudged a turn in the downhill but the race leader and his rival pushed hard on the brakes to avoid a crash. Nieve went straight onto the grass between lorries and camping caravans.
It was nothing more than a scare for Froome, who had three teammates by his side to tackle the two final climbs, the Peyresourde and the Peyragudes ascent.
Nairo Quintana was dropped in the Peyresourde and, with no teammate to bring him back, saw his hopes of winning the Tour vanish. Cummings was then caught with 8 kilometers left, lining up a dramatic finale.