Team Sky's Geraint Thomas extended his lead in the Tour de France as Chris Froome slipped out of second place on 17th stage won by Nairo Quintana.
Froome slipped back off the main group of contenders late on the climb to the summit finish on the Col du Portet before Thomas jumped clear of rivals Tom Dumoulin and Primoz Roglic, who started the day third and fourth in the general classification.
Thomas took third place on the stage behind Irishman Dan Martin, picking up a handful of bonus seconds to go with the time gained on the road.
That means Thomas now leads the Tour by one minute 59 seconds from Team Sunweb's Dumoulin, with Froome two minutes and 31 seconds back.
Froome began to struggle around two kilometres from the top of this imposing climb, losing the wheels as Roglic and Dumoulin drove on the front to try to distance the four-time Tour winner.
Thomas stuck with them, and then burst clear in the final few hundred metres, picking up four seconds on the road to go with four bonus seconds.
Froome drifted back badly despite getting help from team-mate Egan Bernal, finishing 48 seconds behind team-mate Thomas, who now looks in a commanding position with one more mountain test to come before Saturday's time trial.
Quintana, who started the day more than four minutes back in the general classification, hauled himself back into the top five with the second Tour stage win of his career.
The Movistar rider attacked close to the foot of the 16km climb as he followed a move launched by Martin, though he quickly shook off the UAE Team Emirates rider who was left to pursue him alone.
Quintana's victory came despite two early mechanicals on a 65km stage - the shortest road stage in the Tour for over 30 years - that was designed to be explosive from the start.
A Formula One-style grid start turned into something of a damp squib but by the end of the day it appeared Sky's leadership battle had been decisively settled in favour of Thomas.
At one point it looked like going the other way, with Froome following an attack by LottoNL-Jumbo's Roglic midway up the climb, leaving Thomas to sit on the wheel of Dumoulin as the Dutchman worked to shut down the move.
Froome was not alone in cracking on the final climb as AG2R La Mondiale's Romain Bardet and Quintana's team-mate Mikel Landa also fell away. Another casualty on the day was world champion Peter Sagan, who crashed on the dangerous descent off the Col de Val Louron-Azet.
Though he rode to the finish, the Bora-Hansgrohe rider was expected to go for scans, putting at risk a sixth green jersey which is mathematically his as long as he makes it to Paris.