Kennaugh was part of a group of 17 riders who broke away as the peloton headed towards the Côte de Berland on the 168 kilometre stage.

They were able to extend their advantage over the main field to around 6 mins, as they headed toward the Côte de Garcin and Col de Sarenne climbs.

Kennaugh and Ben Swift, a fellow Briton, were able to distance their fellow escapees near the summit of the second climb.

The pair worked together as they climbed Alpe d’Huez, with Team Sky’s Kennaugh able to move clear in the closing kilometres to triumph solo in a time of 4 hours, 43min and 59sec.

Swift would end 13sec behind, with Spain’s Jesus Herrada Lopez completing the top three after finishing 1:11 down.

“It's always hard to win a mountain stage but I have good form ahead of July,” said Kennaugh, a team pursuit gold medallist at London 2012.

“It took us a while to make the break, but once the front group was established I knew I had a good chance.

“To win at L'Alpe d'Huez is better than being an Olympic champion.”

Porte was able to test his general classification rivals further down the road, with the BMC Racing rider accelerating in the closing kilometres.

Denmark’s Jakob Fuglsang was able to follow the attack, but Britain’s three-time Tour de France winner Chris Froome was distanced by the move.

Porte would end 1:56 behind the stage winner, with Froome and Spain’s Alejandro Valverde ending 23sec further back.

It gives Porte a 1:02 lead over Froome heading into tomorrow’s concluding stage, while Fuglsang is third 1:15 behind.

The International Cycling Union WorldTour race will conclude with a 175km stage from Albertville to Plateau de Solaison.