Sir Chris Hoy has claimed if Bradley Wiggins wins the Tour de France then it will be the "greatest sporting achievement" by a British athlete.
Wiggins is almost certain to become the first Briton to win the Tour on Sunday.
The 32-year-old leads Team Sky team-mate Chris Froome by two minutes and five seconds with Italian Vincenzo Nibali a further 36 seconds back.
"If he does it, I think this will be the greatest achievement by any British sportsperson ever," Hoy said.
The four-time Olympic gold medallist continued: "That's a big claim, but you cannot overstate how hard it is to win the Tour de France.
"There's a reason why no-one from Britain has ever done it before. I still have to pinch myself. It's just unbelievable."
Mark Cavendish won stage 18 of the Tour on Friday, his second stage win in this year's event, as Wiggins maintained his advantage over Froome and Nibali ahead of Saturday's 53.5km contre la montre to Chartres stage.
Given Wiggins won the previous time trial in this year's Tour by 35 seconds from team-mate Froome, he will be confident of extending his advantage in the penultimate stage.
Olympic team pursuit gold medallist Geraint Thomas was also full of praise for Wiggins and the Welshman thinks the Team Sky rider's performances will be a boost for British cycling.
He said: "It's unbelievable really, the way he's ridden all year, he's been so consistent. He's ridden phenomenally.
"Like he always does he's delivered the goods and it's just been incredible to watch. I rode Paris-Nice with him and [Tour de] Romandie this year and you can see he's a changed bike rider, he has the confidence and belief and when he's like that there's no stopping him.
"It's great for British sport and I think cycling will continue to grow, it's fantastic for cycling."