Nairo Quintana soloed to victory on stage 18 of the Tour de France in Valloire as Egan Bernal raced away from Ineos team-mate Geraint Thomas while they tried to shake off Julian Alaphilippe on the Galibier.
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Bernal attacked around three kilometres from the summit of the famed climb and pulled out a lead of 32 seconds over the much-reduced group of favourites to move himself up from fifth to second overall, now five seconds ahead of Thomas.
Thomas had tried a dig of his own, bursting off the front of the group with around two kilometres of the climb but this time Thibaut Pinot and Steven Kruijswijk responded, catching him by the summit, with the effort perhaps only serving to limit Bernal's time gains.
That is sure to reopen the debate over team leadership within Ineos once again.
"We wanted it to be hard but the pace wasn't there," Thomas said. "The call was made for Egan to go and hopefully that would kick it off a bit, but it didn't.
"That's when I went as well, just to test. But at least Egan gained some time on everyone else."
The attacks served to distance Alaphilippe who struggled on the steepest gradients, but the Deceuninck-Quick Step rider used his outstanding descending skills to catch the group on the long drop to the finish and even rode through to try a move of his own off the front before being reeled in.
The Frenchman did more than enough to keep his yellow jersey for another day, with his lead now 90 seconds over Bernal, who sits five seconds clear of Thomas in third.
Jumbo-Visma's Kruijswijk dropped one place to fourth, one minute and 47 seconds down, three seconds ahead of Groupama-FDJ's Pinot in fifth.
Alaphilippe will be happy to have hung on for one more day, but his rivals will have taken note of his struggles on the climb as he quickly lost time before the downhill finish worked in his favour.
With summit finishes to come on each of the next two days, others will be confident he is finally cracking after a remarkable run in yellow.
Quintana certainly was a man feeling better.
The Colombian arrived at the Tour as a contender for the yellow jersey but began the day almost 10 minutes down on the general classification.
That meant he was allowed to go in the breakaway on a brutal day in the Alps, with the riders tackling the Col de Vars, Col d'Izoard and the Galibier in 208 gruelling kilometres.
Quintana attacked from a much-reduced group seven-and-a-half kilometres from the top of the Galibier, cresting it one minute 43 seconds ahead of the chasing Romain Bardet before descending to his third career Tour stage win.
"We have worked conscientiously and well, we have moved on and we have not stopped trying," Quintana said.
"I knew it could be a good day for me. In the end we have won the stage victory. We tried with Mikel (Landa) to advance positions, this is a victory for the team."
Tour de France: Stage-by-stage guide
July 26, Stage 19: Saint-Jean-de-Maurienne to Tignes (126.5km)
Stage 19 is a leg-sapping day designed to test the resolve of anyone planning a late move in the general classification. The Iseran - at 2,770m the high point of the Tour - comes in the middle of the stage and casts a long shadow before the shorter climb to Tignes offers an opportunity for attacks.
July 27, Stage 20: Albertville to Val Thorens (130km)
The last chance saloon for GC hopefuls does not look an inviting one. The final climb of the Tour is the 33.4km HC slog up to Val Thorens. If ever there was a Tour designed for a true climber, one with only a handful of time trial kilometres and four HC climbs in the last three days could be it.
July 28, Stage 21: Rambouillet to Paris Champs-Elysees (128km)
There are two big questions on the final day. Will the yellow jersey winner choose a few glasses of champagne or, as Geraint Thomas did last year, prefer a beer or two as they celebrate along the roads of the Parisian suburbs? And which sprinters will have survived the mountains in order to battle it out on the Champs-Elysees?