Dane Jakob Fuglsang soloed to a summit-finish win on stage 16 of the Vuelta a Espana on Monday as Slovenian Primoz Roglic extended his advantage at the top of the overall standings.
Fuglsang, 34, broke away late on the final climb into the thick clouds at 1,600m altitude in northern Spain.
Promising 24-year-old Briton Tao Geoghegan Hart of Ineos came close for a second straight day, digging in to finish second on the third stage in the spectacular Cantabrian Mountains.
Protecting a sizeable overall lead, Roglic ended up stretching his advantage by 23 seconds over his closest challenger Alejandro Valverde to 2min 48sec with just five stages to go.
The former ski-jumper took advantage of a last-climb struggle for the best young rider's white jersey between Miguel Angel Lopez and Tadej Pogacar who are also fourth and third in the overall standings.
Lopez launched a series of aggressive assaults, with Pogacar stoically sticking to his wheel. Roglic did likewise as the 39-year-old Valverde eventually wilted as the race rose into the cloud-line and the temperatures plunged.
"I pulled a few seconds back, and that's a good thing," said fourth-placed Lopez, who earned the nickname 'Superman' after fighting off knife-wielding thieves who wanted his bike during a junior race.
"It looks very equal between us all, in terms of who has the most energy," said world champion Valverde, who remains second. "I won 40 seconds yesterday and lost 20 today. On a stage like that, 20 seconds is nothing."
Roglic seized control of the overall standings by pulverising his rivals on the individual time-trial, and has further demoralised pretenders by thriving on the 'hors categorie' ascent to Los Machucos on Friday and proving relentless through three climbing stages.
"That was a long, hard day again and a real slog to the finish line but it was a good day for us," Roglic said.
"They were really rolling and I was just concentrating on holding on," said Roglic, who looked set to win the Giro d'Italia in May before dropping to third late on the road to Rome.
The main breakaway which included Fuglsang and Geoghegan Hart were caught by a chasing group with 23km to go just before the foot of the final mountain.
At 34, Fuglsang claimed a first major victory earlier at the prestigious Liege-Bastogne-Liege classic in April.
Highly tipped for a tilt at winning the Tour de France, he was forced out with injury.
The Dane broke away with Italian Gianluca Brambilla with less than 6km to go. Fuglsang's Astana team-mates led the peloton.
Fuglsang dropped Brambilla with 4.1km to go with a powerful push.
"I was lucky, I could see the others were wilting, and it was just a case of going for it," Fuglsang explained.
Tuesday brings the second rest day in Burgos, before Wednesday's 17th stage stretches 219.6km south from Aranda de Duero to Guadalajara which includes a sprint near the halfway mark.