Belgian tyro Remco Evenepoel left his Vuelta a Espana title rivals trailing on a foggy climb in the Cantabrian mountains on Thursday on a stage won by Australian Jay Vine of Alpecin.
Stage six left Bilbao for a 181.2km run through the Picos de Europa where rain and fog curtailed any daredevil descending after a downhill pile up within an escape group gave the peloton a stark safety reminder.
The visibly thrilled Vine was an unexpected winner, and revealed his team had carefully planned the attack.
It was the team plan for me to attack on the final climb, it's unreal, said the 26-year-old from Townsville. This is for my wife, he said before quickly adding he would be buying a Corvette for himself.
But Evenepoel was the star of the day, on the first major skirmish between the title rivals.
Often billed as the new Eddy Merckx, Evenepoel leads the overall standings by 21sec from overnight leader Rudy Molard, while Movistar's Spanish rider Enric Mas is third at 28sec.
Evenepoel's teammate Julian Alaphilippe led the peloton both up and down the penultimate climb before unleashing his young charge on the last one.
A sustained acceleration from Evenepoel on the foggy slopes of Pico Jano, dropped Simon Yates, Richard Carapaz and Primoz Roglic, but, with visibility limited to a few metres on the summit, he could not quite close the gap on Vine, who held on to win by 15sec.
I'm really happy and proud. It's a big dream coming true, said Evenepoel who was tipped for the top three years ago but fell into a ravine in Italy.
What I'm showing today is one of the best things I actually did on a bike. Uphill finish and putting in a strong performance thanks to the team is a dream come true. I hope we can keep it up, he said.
Pre-race favourite Roglic of Jumbo finished the final 12.6km climb 1min 22sec adrift of the 22-year-old Evenepoel (Quick-Step), who also picked up bonus seconds.
There's still a long way but today we lost a bit. (The others) go strong but I didn't need that proof. Quite difficult weather for the Vuelta.
Three-time defending champion Roglic is fourth at 1min 01sec, while Ineos pair Pavel Sivakov and Tao Geoghegan Hart are at 1min 27sec.
Friday's stage seven is a medium mountain run from Camargo to Cisternia, but Saturday and Sunday take the Vuelta into two crucial mountain stages.
A day off Monday will be followed by a long individual time-trial where Evenepoel, on paper at least, should punish his rivals again before the Vuelta swoops into the sultry south.
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