Defending champion Geraint Thomas lost more time to Tour de France leader Julian Alaphilippe as Thibaut Pinot won stage 14 on the Col du Tourmalet.
Britain’s Thomas was dropped by the lead group with around 1km to go before Frenchman Alaphilippe crossed the line six seconds after compatriot Pinot.
Thomas stays second overall, but is now two minutes and two seconds behind Alaphilippe with seven stages left.
Adam Yates also lost time, to slip out of contention for a top-10 finish.
A short but brutal stage delivered all the anticipated drama and was decided at the end of a 19km climb up to the finish line on the summit of Tourmalet, one of the Tour’s most iconic mountains.
It was seen a true test of Alaphilippe’s credentials as a Tour winner and, just as in Friday’s time trial, he exceeded expectations and extended his lead.
After the last escapee from an early breakaway was reeled in halfway up the final ascent, the contenders for the general classification fought it out for the stage win.
Alaphilippe was initially content to stay on Thomas’s wheel as the lead group was slowly whittled down to fewer than a dozen riders.
The 27-year-old, seeking to become the first home winner of the Tour since Bernard Hinault in 1985, has no pedigree in the high mountains but again showed his strength and character in the toughest conditions.
While Thomas cracked and eventually finished eighth, Alaphilippe crossed the line in second place to earn a time bonus that sees his overall advantage over the Welshman increase by 36 seconds.
With more mountain stages to come in the final week of the race, Thomas is not yet out of contention for the yellow jersey but also faces a fight for a podium finish.
Steven Kruijswijk, who finished third on Saturday in the same time as Alaphilippe, is now only 12 seconds behind the Welshman.
Thomas’s Team Ineos team-mate Egan Bernal, Germany’s Emanuel Buchmann and Pinot have also moved to within 70 seconds of the Welshman overall.
Britain’s Adam Yates started the day in 10th place but his hopes of mounting a strong challenge are over after he was dropped early on Tourmalet, eventually finishing more than six-and-a-half minutes after Pinot.
Yates falls to 18th, but he was not the only rider to suffer damaging losses on the final climb of the day.
Colombia’s Nairo Quintana also fell off the pace before the finish and drops from ninth to 14th, while Ireland’s Dan Martin went from 11th to 16th.
Stage 14 result
1. Thibaut Pinot (Fra/Groupama-FDJ) 3 hrs 10 mins 20 secs
2. Julian Alaphilippe (Fra/Deceuninck-Quick Step) +6secs
3. Steven Kruijswijk (Ned/Jumbo-Visma) same time
4. Emanuel Buchmann (Ger/Bora-Hansgrohe) +8secs
5. Egan Bernal (Col/Team Ineos) same time
6. Mikel Landa (Spa/Movistar) +14secs
7. Rigoberto Uran (Col/EF Education First) +30secs
8. Geraint Thomas (GB/Team Ineos) +36secs
9. Warren Barguil (Fra/Arkea Samsic) +38secs
10. Jakob Fuglsang (Den/Astana Pro Team) +53secs
General classification after stage 14
1. Julian Alaphilippe (Fra/Deceuninck Quick-Step) 56hrs 11min 29secs
2. Geraint Thomas (GB/Team Ineos) +2min 2secs
3. Steven Kruijswijk (Ned/Jumbo-Visma) +2mins 14secs
4. Egan Bernal (Col/Team Ineos) +3mins
5. Emanuel Buchmann (Ger/Bora-Hansgrohe) +3mins 12secs
6. Thibaut Pinot (Fra/Groupama-FDJ) +3mins 12secs
7. Rigoberto Uran (Col/EF Education First) +4mins 24secs
8. Jakob Fuglsang (Den/Astana Pro Team) +5mins 22secs
9. Alejandro Valverde (Spa/Movistar) +5mins 27secs
10. Enric Mas (Spa/Deceuninck Quick-Step) +5mins 38secs