"For sure I'm not going to sit up and lose time, but I think we're in a great position".
But Sky kept their powder dry until Thomas launched his move.
There will be two more stages in the Alps with a summit finish at the iconic Alpe d'Huez, but fireworks should not be expected as the top guns are likely to hold fire, waiting for the finale in the Pyrenees.
Thomas leads the race overall from Froome by one minute 25 seconds. "It's the ideal scenario at the moment and long may it continue".
"I knew there was a good chance". Obviously Froomey is the leader, he's won six Grand Tours. "If I have to pull towards the end, then I will", Thomas said.
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His third public plea comes after it was reported that he is planning to fly to the U.K.to see his daughter, whether she wants to or not.
But Thomas and Sky have played that down.
While he seized the moment to attack the main protagonists in the mountains, his courageous ride is only likely to have extended his stay in yellow for 24 hours, as the Tour continues with another day for the climbers on Wednesday.
It will be a second spell in yellow for Thomas, who won the opening time trial of last year's Tour in Dusseldorf.
The Australian fractured his collarbone in an early crash and abandoned the race for the second year in a row.
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.
After going up the beyond-category ascents to Montee de Bisanne and Col du Pre, plus the second-category Cormet de Roselend, the stage concluded with the unprecedented and lengthy 17.6-kilometre climb to La Rosiere - a ski resort linked to La Thuile in the Italian region of Valle d'Aosta.
Thomas then attacked again, blasting past yellow jersey contender Tom Dumoulin and then Mikel Nieve to win the stage and deliver a huge statement.