Thomas sits second to Greg Van Avermaet in the general classification after nine stages, 43 seconds off yellow but 59 seconds ahead of Froome as the race heads towards the Alps. "When they go, it is never nice to see them all riding away but we had confidence in each other and we rode really well".
Behind him, the GC contenders kept their powder dry as Team Sky controlled the pace in the peloton, as Geraint Thomas, Chris Froome and Mitchelton-Scott's Adam Yates also finished safely in the GC group.
The 12th stage at the Tour de France, the 175.5km run from Bourg-St-Maurice Les Arcs to Alpe d'Huez gets under way at 11.10am (BST) and is scheduled to reach KMO at 11.25am.
"One of them may crash one day so they will not want to give up their option, they will want to race first as second as long as they can". It's just a bit of an unknown for me to race over three weeks.
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Thomas said: 'It's unreal, I didn't expect it at all. He knows how to race over three weeks.
Alaphilippe now leads the King of the Mountain standings and will wear the polka dot jersey during Stage 11.
It will be a second spell in yellow for Thomas, who won the opening time trial of last year's Tour in Dusseldorf.
Julien Alaphilippe has become the first home stage victor in this year's tour, after a long-range attack in the mountains of the Haute Savoie led to a solo win in Le Grand-Bornand. "Maybe two years ago I would have attacked too early".
Thomas attacked with a little more than 5.5 kilometres left of what was a pulsating 108.5 kilometre stage from Albertville to La Rosiere, which included four categorised climbs, the first two of those classified as Hors-Categorie. Dumoulin then escaped from the peloton with a downhill attack from Cormet de Roselend and joined up with Valverde on the final climb.