Onley produced a superb ride on Thursday’s stage 18, battling with Pogacar and Vinegegaard until the last few hundred metres of the final climb up the mighty Col de le Loze in Courchevel.

In the end the 22-year-old from Kelso in the Scottish Borders came fourth, but finished one minute 39 seconds ahead of the man he is chasing for third place overall, the white jersey wearer Florian Lipowitz.

Onley was dropped on the penultimate climb on Thursday and it looked as though 24-year-old German Lipowitz would extend his advantage over the Team Picnic PostNL rider.

But with the help of his team in the valley, he was able to re-join the main favourites and when Lipowitz, who had attacked, cracked on the 26.5km final climb, Onley produced a staggering performance for such a young rider as he clung on to Pogacar and Vingegaard to slash Lipowitz’s advantage.

Friday’s stage being shortened might affect the Team Picnic-PostNL rider’s chances of catching Red Bull-Bora-Hansgrohe’s Lipowitz – but with the race staying in skiing country, the monstrous 19.4km final climb to La Plagne could still see significant time differences.

Defending champion Pogacar and Denmark’s two-time winner Vingegaard have won the past five Tours between them.

The top two are well clear of the rest – but world champion Pogacar looks in a class of his own and starts the stage with a commanding four minutes 26 seconds lead over his rival from Team Visma-Lease A Bike.

The race concludes on the Champs Elysees in Paris on Sunday.