Persistence 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.

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There was no change in the overall standings a day ahead of a massive mountain slog, with Jumbo's Primoz Roglic staying 21 seconds ahead of defending champion, Colombian 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 him at Laruns at the end of Sunday's stage nine.

The Sunweb man finally found the right formula with 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 kilometer I still didn't allow myself to hope," said the 2018 under-21's world road race champion.

"I was so close twice. And on Sunday I got caught 1.6km from the line. But there was sadness because I lost the sprints twice. It was tactics that let me down," he said.

Hirschi was given a late scare again by Alaphilippe but 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 goes climbing on Friday seven ascents culminating with 1,783m up the extinct volcano of Puy Mary in the Massif Central.

"Our team needs a win," Bernal said.

"The final 2km are really steep and there will be time differences for sure, so we need to get there with fresh legs."

Volcano Stage Threatens to Erupt

Leader Roglic offered a deadpan analysis.

"The Puy Mary looks very difficult, so it'll be a great challenge," he said.

The Puy Mary is a 15km climb to a summit finish with gradients of 9 percent.

"We are expecting a major battle from our rivals up there, but we are just planning to race our own race," said the 30-year-old who won the Vuelta Espana last year.

Bernal appeared a little washed out Thursday but suggested he was looking forwards to measuring himself against the leader.

"There have been some fairly stressful days trying to avoid falls, in the wind and the sprints," said the man who cut his own hair to comic effect on Monday.

"I'm looking forwards to the mountains now. I feel a bit stronger every day," said the slightly-built Bernal," who snatched the yellow jersey on stage 19 in 2019 Tour de France.

Hardy fans will be welcome to climb Puy Mary on foot, but no vehicles will be allowed on the slopes.

- Presidential run -

Thursday's stage was held in the presence of one former president, Francois Hollande, who hails from the verdant Correze region, and paid homage to another, the recently deceased Jacques Chirac who came from the arrival town Sarran.

The Tour also remembered one of its favorite sons Raymond Poulidor, who never won the race or wore its yellow jersey, but became a national hero for coming second or third eight times.

There was heartening news for the four teams cowering beneath the dangling Sword of Damocles final round of COVID tests to be held next Monday.

The original ruling of two strikes and you're out has been adjusted, so only teams returning two more positive tests will be excluded. Ineos, FDJ, Mitchelton-Scott, and CCC all had one positive among their staff last Monday.