Christophe Riblon picked the perfect day for his second Tour stage win of his career, conquering the double ascent of Alpe d'Huez to become the first Frenchman to enjoy a victory on the centenary Tour.
Britain's Chris Froome extended his overall lead despite struggling on the second gruelling climb of the famous 21 hairpin turns, even calling desperately for an energy bar in the final five kilometres.
His request for Richie Porte to retrieve the energy bar from the Team Sky car contravened Tour rules and saw him lose 20 seconds as a penalty.
While he saw off Alberto Contador's attacks to finish ahead of the Spanish rider, Froome will be a little concerned by the ominous performance of Nairo Quintana, who left him behind to finish more than a minute ahead of the Tour leader.
The result still leaves Froome clear of second-placed Contador by five minutes and 11 seconds with Quintana rising to a podium place a further 21 seconds adrift.
The day, though, undoubtedly belonged to Riblon, who saw off Tejay van Garderen on the final climb to race clear for an historic victory in the 100th year of the Tour.
It was the first time the celebrated Alpe d'Huez had been climbed twice on the way to the stage finish in the race's history.
Riblon crossed the line all alone with arms aloft after catching American Van Garderen two kilometres from the finish and racing away to win by 58 seconds.
The 32-year-old won despite being the only man to come to grief on the much-feared descent of the Col de Sarenne today, riding into a ditch before clambering back to the road.
Froome finished seventh alongside Richie Porte in sixth, and although he surrendered a little over a minute to Quintana, he can be happy to have seen his overall lead increase once again on such a dangerous stage.
With the forecast thunderstorms staying away, Contador had attacked Froome on the feared descent of the Col de Sarenne which linked the two ascent of the Alpe.
Throwing caution to the wind, he and team-mate Roman Kreuziger pulled 20 seconds clear, but could not stretch it any further and instead sat up to be caught before the second climb.