Geraint Thomas has admitted Stage 17 could make or break his bid to become the first Welshman to win the Tour De France.
The Team Sky rider will wear the yellow jersey on a brutal 65km route that includes four long ascents over three mountain passes and will require two hours of solid climbing.
If Thomas is to crack – as he has at times before on previous tours, although always in the service of team leaders – then this is the stage where his rivals will bid to make it happen again.
It could be the end of his hopes of glory, but just as likely he could win an incredible third mountain stage.
Thomas is not alone in never having raced a comparable stage on any previous tour and the former member of Maindy Flyers junior club in Cardiff admits the journey into the unknown will severely test his attempt to stay ahead of Chris Froome and the rest of the chasing pack.
He said: “It’s going to be massively decisive. It’s the first time we’ve ever done a stage like that, there’s a good two hours of climbing which is a lot over such a short period of time.
“We’ve got to be clever with it. There’s no point in going too hard from the start because you can run out of legs on that last climb, which is possibly the toughest climb of the Tour. It’s a big, big day and for sure there are going to be some splits.
“Everyone is a bit apprehensive about it. You can’t get carried away because that final climb is possibly the toughest climb of the Tour.”
The other novel feature of Wednesday’s stage is a grid start which sees the leading riders placed at the front.
Some riders have dismissed it as a gimmick and Thomas believes it will have little effect on how the day unfolds.
“There will be some attacks but I’m not so sure that the grid start will affect the race so much.
“Obviously, if some of the guys in the top 10 go it will be a gutsy move, and there are a few guys you’d expect to go more than others but to go from the start would be risky for sure. We’ll just to need to ride it together.”
Thomas leads Sky teammate Froome by 1:39, with Dutchman Tom Dumoulin 11 seconds further back before Wednesday’s savage trek that ends with the much-feared climb up the Col du Portet, a lung-busting 16-km ascent at an average gradient of 8.7 percent.
The potential for drama follows drama of a different type on Tuesday after farmers blocked the 16th stage and forced several riders, including Thomas, to receive treatment for tear gas.
Farmers protesting about the loss of rights for agricultural land in the Aude region blocked the road with bales of hay and around 50 sheep some 26 kilometres (16 miles) into the day’s ride from Carcassonne to Bagneres-de-Luchon in the Pyrenees.
In their efforts to clear the protestors, officers from France’s national gendarmerie used tear gas, which was blown into the faces of dozens of riders as they approached.
“Obviously it was unfortunate that whatever they used was still in the air when we came through,” said Thomas.
“I felt a tingle in the eyes, and in the back of my throat. I used some water to wash it out. But I was alright in the end.”
Television images showed Tour de France medical officers handing out eye drops to riders including green jersey points leader Peter Sagan.
“It was like pepper spray that got it in your eyes and affected your breathing, not directly, but it was in the air,” said Slovakian Sagan, of the Bora team.
“But after 10 minutes, everything was okay.”
This year’s Tour de France has been marked by a series of incidents on the sidelines including abuse directed at Team Sky and Froome.
Amid a general feeling of frustration surrounding Sky and their sheer domination of the race, Froome has been spat at and manhandled, Thomas has been booed off the podium, and some of Sky’s staff have also faced abuse.