Sticking his tongue out in apparent exhaustion, it was a strong signal that Froome has reached his limit after winning the last three Grand Tours - the Tour and Spanish Vuelta past year and the Giro d'Italia in May. Froome prevailed in both.
Four-time champ Chris Froome said he "just felt throat and nose were burning, eyes were burning afterwards".
The incident prompted an angry exchange between Froome and the police officer, before the Sky rider rode away. Either way, he rode the.
They only had to control Dumoulin and Lotto Jumbo rider Roglic, who launched a series of attacks in the closing kilometres that put Froome in trouble.
"Thomas has been the strongest, and that's the situation now", Dumoulin said.
"'G' (Geraint) has ridden such an fantastic race and he deserves to be in yellow - and, fingers crossed, he holds it now until Paris".
Stephane Mahe Reuters
A Formula One-style grid start turned into something of a damp squib but the final climb appears to have provided one of the decisive moments of the Tour.
Despite feeling so good on the daunting 16km climb at an average gradient of 8.3 per cent, Thomas was not tempted to attack earlier, aware of how he could be affected by altitude - 2,215 metres at the summit.
On Friday, Thomas and Froome will be praying they successfully negotiate a 19th stage featuring six categorised climbs. "I chose to bring young Egan (Bernal) here and then half way through I thought I might really regret that decision - and that was nothing to do with racing his bike, or performance, it was just about the experience he was having".
Froome's struggles, however, gave him the confidence to power on.
But the Dutchman did his best not to give up hope of catching Thomas.
But as the Giro d'Italia in May showed, a faltering Froome may also be like a badger, at his most threatening when cornered. "I think that's the main reason for our success so far at this Tour".
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