Persistance finally paid off for Marc Hirschi as the Swiss soloed to victory on stage 12 of the Tour de France on Thursday, putting behind him two gut-wrenching near misses.

There was no change in the overall standings a day ahead of a massive mountain slog with Jumbo's Primoz Roglic 21 seconds ahead of defending champion Colombia's Egan Bernal of Ineos.

The 22-year-old Hirschi was first pipped at the line by flying Frenchman Julian Alaphilippe on Nice's iconic Promenade des Anglais on stage two.

He then suffered another blow when the Slovenian pair Tadej Pogacar and Roglic caught and beat him at Laruns in Sunday's stage nine.

But the Sunweb man finally found the right formula to produce a heroic long-range solo victory on the Tour's longest stage of 218km from the chateau-dominated town of Chauvigny over four rolling hills to Sarran in central France's pastoral heartland.

"I haven't been sleeping well and I had a bad back but I said to myself just go for it," said the bearded escape artist.

"I never would have believed it and even in the final kilometre I still didn't allow myself to hope," said the 2018 under-21's world road race champion.

"I was so close twice, so it's an unbelievable feeling."

Hirschi was given a late scare again by Alaphilippebut the Frenchman quickly abandoned his late pursuit.

"He deserved his win, I'm glad for him, I just didn't have the legs. He was too strong," Alaphilippe said at the line.

The Tour takes in Europe's largest volcano Friday with the 70km in diameter Puy Mary on the Cantal Massif with the peloton to ascend to 1783m.

"Our team needs a win," Bernal warned at the finishing line Thursday.