Poland's Rafal Majka took a big step towards winning the Tour de France polka dot jersey when he took a solo route to the stage victory overnight as Italian Vincenzo Nibali strengthened his grip on the overall race.
Majka was the best climber on the 17th stage, a brutal 124.5-km trek from St Gaudens featuring four tough ascents, and extended his lead over Nibali and Spain's Joaquim Rodriguez in the mountain classification.
The win was his second stage victory after prevailing on the 14th stage in the Alps, and a third in four stages for Tinkoff-Saxo after leader Alberto Contador crashed out.
"I'm so happy because my team worked so hard for that result," said Majka, who has 149 points in the mountain classification.
Nibali has 118 and Rodriguez 112 with 80 points left up for grabs.
Italian Giovanni Visconti was second with Nibali taking third place to extend his overall race lead to over five minutes.
"It was a nervous stage, I'm relieved," the calm Nibali said.
France's Jean-Christophe Peraud was fourth as he gained more than 50 seconds on compatriot Thibaut Pinot, who struggled in the final climb.
"In the third week, it's difficult everyday but I'm happy I can hold Nibali's wheel," said the 37-year-old Peraud.
Nibali leads Spain's Alejandro Valverde by 5:26 with Pinot in third place overall, six minutes off the pace. Peraud, who is expected to fare better in Sunday's time trial, lies fourth, eight seconds behind Pinot.
A group of 22 riders, featuring Rodriguez, Majka, Luxemburg's Frank Schleck and Dutchman Bauke Mollema, who started the day in 10th position overall, broke away at the foot of the Col du Portillon, the first of four brutal climbs.
A Movistar soigneur (caretaker), on the climb to hand out drinks to the riders, tangled with Australian Luke Durbridge (Orica GreenEdge), who fell off his bike, but remounted to continue the stage.
Vasil Kiryienka of Belarus powered away from the leading group and was first to crest the top of the Col de Peyresourde, but he cracked in the penultimate climb up the Col de Val Louron-Azet.
Majka burst away from the breakaway group as he looked to strengthen his lead in the mountain classification.
Bardet attacked in the descent from the Col de Val Louron-Azet and opened a 30-second gap over Pinot, Nibali, Valverde, Peraud and Tejay van Garderen.
Once Bardet was caught on the final climb, Nibali attacked 5.5 kilometres from the finish as Valverde cracked.
Peraud was in the Italian's wheel while Pinot, Bardet and Van Garderen chased.
Nibali and Peraud opened a decent gap and Pinot and co limited the damage but could not catch the duo.
Valverde, who at one point lagged some 20 seconds behind the Pinot group, was helped on the way by a few Movistar team mates who had been dropped from the morning's breakaway.
He fought his way back in the 10.2-km ascent and gained a handful of seconds on Pinot.
"I had a bad moment, but there were some team mates to help me," said Valverde.
"I found my rhythm again and managed to limit the damage."
The 24-year-old Pinot now has Friday's 18th stage to Hautacam to regain time on Peraud and Valverde.
"The ascent to Pla d'Adet did not really suit him, but he likes the climb to Hautacam," his FDJ.fr sports director Yvon Madiot said.
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