He lost 52 seconds to his Sky team-mate, who will surely now be confirmed as their No 1 rider despite the team's previous insistences that they would share their load equally - Froome has slipped to third, two minutes and 31 seconds off the lead compared to Dumoulin, who is just under two minutes away.
Julian Alaphilippe secured his second stage victory of the Tour de France on a day where the race was briefly interrupted by a farmers' protest and pepper spray.
Team Sky boss Sir Dave Brailsford has apologised for saying the hostile reception they have faced at the Tour de France is a "French cultural thing". "But if we're able to mix the strain of longer stages with shorter legs that allow space for more attacks, a good mix could be the victor".
The last time a Tour stage was blocked by a demonstration was in 2004.
Colombian climber Nairo Quintana won the short but extremely hard mountainous stage with a solo attack up the brutal finishing climb to Col du Portet.
"I'm a Francophile", he said.
"I was not affected because I was not in the first 10 of the group", he said.
Rangers Trading Cole Hamels To Cubs
With the Cubs over the last two seasons, he has an ERA of 3.98 in 11 starts and 10 relief appearances. The 34-year old has had a rough season with a 5-9 record with a 4.72 ERA and 1.37 WHIP.
I don't quickly see that happening, Froome winning the Tour, but like you see in the Giro, anything is possible in the last days, but I'm focusing on myself and not on Froome.
"We feel safe. Obviously on some of the climbs not everyone's our fans but we don't feel threatened", Thomas said.
It was a scary moment, especially since that particular pass is where cyclist Fabio Casartelli crashed during the 1995 Tour de France.
"I waited a bit for my own attack, but I didn't have the legs to drop Thomas and Roglic, I was happy I could stay with Roglic; Thomas was just the strongest".
At one point it looked like going the other way, with Froome following an attack by LottoNL-Jumbo's Roglic midway up the climb, leaving Thomas to sit on the wheel of Dumoulin as the Dutchman worked to shut down the move.
"We just got to look after (Thomas) now", Froome said.
The Bora-Hansgrohe rider described the incident in typically colourful fashion before confirming his intention to race on, needing only to make it to Paris now to confirm a sixth career green jersey.
"I had a bad kilometre between three and four to go and he pulled the gap out and I couldn't close in the end".