Impey hopes to defend lead

The 195km trek starts from Castres stays flat for a long time before ending with two huge climbs.

First up is the Col de Pailheres - a ferociously tough ascent that goes on for about nine miles at a gradient of eight percent - and then a shorter but even steeper ride to the finish at the ski resort of Ax 3 Domaines.

Tour contenders Chris Froome and Alberto Contador could launch their first significant attacks of the race and take the yellow jersey off Impey, who is not a challenger and said himself that he expects to struggle in the mountains.