Julian Alaphilippe of Team Quick-Step climbed brilliantly to secure victory in Stage 10 of the Tour de France, as the race hit the Alps for the first time.
Overall leader Greg Van Avermaet was part of the breakaway group for large parts of the stage and finished just under two minutes behind Alaphilippe to retain the yellow jersey.
Team Sky riders Chris Froome and Geraint Thomas remained in the peleton for the duration of the stage and are now over two minutes behind Van Avermaet in General Classification.
As the tour headed to the mountains for the first time following Monday's rest day, a group of 21 riders including Van Avermaet broke early from the peleton.
The Belgian rider was joined in the lead by fellow General Classification contender Philippe Gilbert and green jersey leader Peter Sagan, but Team Sky riders Geraint Thomas and Chris Froome remained behind.
The 158.5 km stage from Annecy to Le Grand-Bornard featured three category one climbs, including two in the final 30 km.
The first of the day, at Col de la Croix Fry, was won by Rudy Molard (Team Groupama-FDJ), with Gilbert and Van Avermaet in 5th and 6th respectively.
Sagan had already picked up maximum points in the intermediate sprint at Thones to extend his lead over Colombian Fernando Gaviria in the sprinters standings.
The second climb of the day to Plateau des Glieres featured a section on dirt roads. Alaphilippe led the breakaway group to pick up maximum points while further back in the peleton, Froome suffered a puncture on the rough track to fall farther behind.
Froome recovered quickly to rejoin teammate Thomas, but the Team Sky riders had fallen almost seven minutes behind Van Avermaet and the breakaway group.
With 30 km to go, the pace of the breakaway group quickened at the bottom of Col de Romme, the penultimate climb.
Several riders, including Gilbert, were dropped quickly into the climb. Alaphilippe picked up his second win ahead of Rein Taaramäe, with Van Avermaet dropping back to around 90 seconds behind.
Alaphilippe increased his lead over Taaramäe in the descent before the final climb of the day, Col de la Colombiere, and with 20 km to go the French rider was 20 seconds in front.
As the climb began, Alaphilippe increased the pace again while Taaramäe fell away. Alaphilippe, who is already out of General Classification contention, was over one minute ahead as he reached the top of the Colombiere.
All that was left for Alaphilippe to do was descend the remaining 14 km to Le Grand Bornard, crossing the line one minute and 34 seconds ahead of Ion Izaguirre Insausti for his first Tour de France stage win.
Alaphilippe now leads the King of the Mountain standings and will wear the polka dot jersey during Stage 11. He also became the first French rider to win a stage this year.
Stage results
1. Julian Alaphilippe - 04:25:27
2. Ion Izagirre - +00:01:34
3. Rein Taaramäe - +00:01:40
4. Greg Van Avermaet - +00:01:44
5. Serge Pauwels - +00:01:44
General classification
1. Greg Van Avermaet - +40:34:28
2. Geraint Thomas - +00:02:22
3. Alejandro Valverde - +00:03:10
4. Jakob Fuglsang - +00:03:12
5. Bob Jungels - +00:03:20