Julian Alaphilippe's descending skills made the difference as the Frenchman claimed his second victory in this year's Tour de France to take the 16th stage on Tuesday.
The Quick-Step Floors rider, who already prevailed in the 10th stage in Le Grand Bornand, whizzed past Adam Yates six kilometres from the line after the Briton had hit the asphalt in a left-hand curve in the final descent.
Spain's Gorka Izagirre took second place and Yates finished third, 15 seconds behind.
The stage was briefly interrupted with 187km to go by a farmers' protest, police using tear gas to disperse the demonstrators with some riders being affected.
Among them was world champion Peter Sagan and Briton Geraint Thomas, who retained the overall leader's yellow jersey after an otherwise comfortable 218-km mountain ride from Carcassonne.
Thomas still leads his Team Sky mate and defending champion Chris Froome by 1 minute, 39 seconds and Dutchman Tom Dumoulin by 1:50 going into Wednesday's 17th stage, a brutal 65-km, up-and-down trek from Bagneres-de-Luchon to Saint-Lary-Soulan.
Downhills were tricky on Tuesday and former world champion Philippe Gilbert went spectacularly over a low stone wall in the descent from the Col du Portet d'Aspet. The Belgian got back on his bike after disappearing in the ravine for a couple of minutes.
It was in the same descent that Italian Fabio Casartelli crashed and died in the 1995 Tour de France.
"It's pure happiness after a day of suffering," said Alaphilippe, who tightened his grip on the polka dot jersey for the mountains classification.
Alaphilippe fought hard to get his place in the day's large breakaway and he produced his effort at the right moment to be the second rider to reach the top of the Col du Portillon, 20 seconds behind Yates.
He was gaining time in the descent when Yates went down.
"I knew the last kilometres of the stage. I'm sad for Yates who crashed but it could have happened to me. I took a lot of risks. It's bike racing," the Frenchman said.
A breakaway of 47 riders took shape after the race was briefly interrupted by the farmers' protest.
"Please respect the riders, even if you have a cause to fight for," said Tour director Christian Prudhomme.
The stage resumed after a 15-minute interruption and Alaphilippe stayed quiet in the breakaway group until the last climb to the Col du Portillon.
Sagan virtually secured a record-equalling sixth green jersey for the points classification, which he will officially wrap up if he reaches Paris. He leads Norway's Alexander Kristoff by 282 points with 270 still up for grabs.
