Adam Yates became the first British winner of the San Sebastian Classic on Saturday with the Orica rider also claiming his maiden title at the major level.
The 22-year-old went into the race on the back of a 50th place finish in the Tour de France.
Philippe Gilbert, the 2011 winner from Belgium, was second just ahead of Spain’s defending champion Alejandro Valverde.
Yates won by 15 seconds after reeling in a late escape launched by young French rider Warren Barguil on the race’s final climb, the col de Bordako Tontorra, seven kilometres from the finish.
“Incredible,” Yates said. “I won, but I didn’t know I had won.”
“I spoke on the radio to my sport director but because of the crowds the radio was too quiet.
“On the final climb there was a breakaway still up the road. Then there was a lot of carnage on the climb, there was a crash with a motorbike, and so I just went full gas.
“At the time I didn’t know if I had reached the lead or not.”
It was a memorable day for the winner as twin brother and teammate Simon Yates came home in a respectable 14th spot inside the trailing group, all timed at 15sec behind.
Valvede, who was also the 2008 champion, increased his lead in the overall World Tour 2015 rankings ahead of Tour de France champion Chris Froome and fellow Spaniard Alberto Contador. – Agence France-Presse