France's Thibaut Pinot drew upon all his climbing credentials to win stage 15 at the Tour of Spain but Britain's Simon Yates extended his overall lead by finishing third on Sunday.
Pinot, of Groupama, came in 28 seconds ahead of Astana's Miguel Angel Lopez and 30 in front of Yates, of Mitchelton, to claim his first stage win at this event.
After already clinching one stage at the Giro d'Italia and two at the Tour de France, Pinot becomes the 18th active rider to have completed the set of wins at all three Grand Tours.
At the top of a fog-smothered Lagos de Covadonga, he punched the air as he crossed the line first, a reward for breaking away from the group of favourites with six kilometres left.
Yates, however, was not far behind and he now leads Spain's Alejandro Valverde by 26 seconds in the general classification and Colombia's Nairo Quintana, also of Movistar, by 33, following a third consecutive summit finish.