Chris Froome extended his Tour de France lead on the climb to Finhaut-Emosson, strengthening his grip on the yellow jersey.
The Brit finished 11th on stage 17, 7mins59s behind winner Ilnur Zakarin, but crucially crossed the line 40s ahead of his closest rival, Bauke Mollema.
Froome, searching for a third Tour de France title and second in a row, now leads the Trek Segafredo rider by 2min27s in the overall standings, with just four stages remaining – including the procession into Paris on Sunday.
BMC Racing rider Richie Porte attacked the group of main contenders on the final climb of the 184.5km stage in the Swiss Alps.
Froome’s teammate, Wouter Poels, countered the attack, dragging the leader up to Porte and, in the process, dropping the remainder of the group, including Movistar’s Nairo Quintana and Orica BikeExchange’s Adam Yates.
Poels faded in the final stages as Froome and Porte rode clear, with Yates attacking the group behind and putting time into both Quintana and Mollema.
Froome, who now just has three real stages to negotiate before claiming a third Tour title on Sunday, credited his hard-working team on what was a scorching day in the Alps.
"It was very difficult because of the heat," said Froome. "But my team were incredible, they did an amazing job and I was able to stay with the best.
“I don't think it was possible to go faster than Richie at the end. I didn't need to pull. Today was only the first of a block of four difficult days in the mountains.
“The main difference between Team Sky and the other teams is that my eight team-mates are focused on one goal only, which is to help me win the Tour de France while other teams have two GC riders or a sprinter or someone to go for breakaways.
“Leading the Tour de France is about dealing with being in the yellow jersey and going to the press conference every day.
“At the beginning, you feel the pressure when you find yourself in this position. Now it's easier, I'm more relaxed.”
Yates remains in the white jersey for best young rider, as well as third in the overall standings, 2min53s down on Froome, but closed the gap on Mollema to just 26s.
The Lancastrian is also 34s ahead of Colombia’s Quintana, who has twice finished as a runner-up at Le Tour.
Tomorrow sees the peloton tackle a 17km uphill time trial from Sallanches to Megeve.
Sportsbeat 2016