Britain's Chris Froome moved to within touching distance of a third Tour de France title by increasing his lead over his main rivals in the race’s 17th stage.
Froome dropped Colombian Nairo Quintana and Dutchman Bauke Mollema in the later stages of a punishing final climb as he extended his advantage in the general classification to two minutes and 27 seconds.
The Team Sky rider must now navigate three more dangerous stages in the Alps, including Thursday’s final time-trial, before the formality of Sunday’s procession into Paris.
Russian Ilnur Zakarin claimed a breakaway victory in Finhaut-Emosson, in a stage held entirely in Switzerland for the first time.
“There was no real need to get on the front tactically. Obviously it was the first day of a four-day block, [Thursday] is going to be critical,” said Froome, who finished on the wheel of former colleague Richie Porte.
“Quintana tried one time to attack but maybe he didn’t have the legs like last year. It was tough but I’m happy to follow the best – Richie Porte was very strong on the final climb.”
Trek-Segafredo’s Mollema is the closest challenger to Froome for the yellow jersey, with Orica’s young Briton Adam Yates a further 26 seconds behind in third place overall.
Quintana is fourth, three minutes and 27 seconds adrift of Froome, while Australian Porte, now with BMC Racing, is another minute off the pace but boosted his podium chances with a strong display in Switzerland.
Zakarin, who served a two-year doping ban in 2009, was part of an initial breakaway and then joined an attack by Pole Rafal Majka and Colombian Jarlinson Pantano before leaving them both trailing on the last ascent.