Lilian Calmejane fought off a bout of cramp to claim a dramatic solo win in the eighth stage of the Tour de France.
The race's overall favourites remained quiet on the eve of a punishing day in the Jura mountains.
The 24-year-old Calmejane, in only his second year as a professional, dropped his breakaway companions in the last climb of the day and despite cramping up in the closing stages, held off Dutchman Robert Gesink for a second grand tour stage win.
Another Frenchman, Guillaume Martin, took third place.
Chris Froome had a minor scare when he went off the road in a descent but the Team Sky rider kept his cool in sweltering heat to retain the overall leader's yellow jersey.
Froome leads the general classification by 12 seconds from fellow Briton Geraint Thomas, with Italian national champion Fabio Aru of Astana third, 14 seconds back.
Irishman Dan Martin, fourth overall at 25 seconds back, tried a late attack as the flamme rouge approached but the Quick-Step Floors man was quickly shut down by Sky.
Calmejane of Direct Energie kept his strategy close to his chest in the day's breakaway, but barely looked back after pulling away in the 11.7km climb to La Combe de Laisia.
Gesink (LottoNL-Jumbo) chased hard but the Frenchman had too much power in the finale.
Calmejane, almost came to a halt five kilometres from the line, however, due to cramp in his right thigh.
"It's huge. It was everything I was dreaming of," said Calmejane, who won a stage in last year's Vuelta.
"When I had cramp in the finale, I decided to drop a gear so I could pedal softer," he said.
Team Sky were in control all day despite a hectic start to the stage, with almost 50 riders managing to break away from the main pack.
They will be further tested on Sunday, when the ninth stage takes the peloton through the Jura mountains with three lung-busting climbs in prospect before a dangerous descent to Chambery.
The 4 New Zealanders remain in the tour.