Geraint Thomas delivered a major statement of intent in the defence of his Tour de France crown as he dropped Ineos team-mate Egan Bernal on the final brutal slopes of La Planche des Belles Filles.
As Dylan Teuns won stage six from the breakaway and young Italian Giulio Ciccone snatched the yellow jersey off the shoulders of Julian Alaphilippe, it was the sight of Thomas defying his own predictions and powering clear of the main contenders at the last which caught the eye.
Much had been made of the five seconds the 22-year-old Bernal picked up due to a momentary lapse from Thomas in the finale of stage three in Epernay, and the gap between the team's co-leaders was only expected to grow here as gradients hit 24 per cent and the surface turned to gravel.
Thomas spent Wednesday explaining why the stage did not suit him and pointing to Bernal as one of the favourites to profit, but the wily Welshman perhaps knew more than he was letting on.
"I was feeling good but I was unsure," Thomas said. "I thought the steep climbs weren't my cup of tea. I was expecting others – (Nairo) Quintana, Egan, (Adam) Yates – would jump up there. It was a decent day in the end.
"It is one of those climbs where you have to patient. When Alaphilippe went clear at 800 (metres to go), quite early, I had the confidence to let him go and ride my own tempo and drive it all the way to the line from 350. I was starting to blow though. It is decent."
Decent would be an understatement for the day as a whole as it delivered the drama organisers had promised over seven categorised climbs and more than 4,000m of ascent.
Bahrain-Merida's Teuns and Trek-Segafredo's Ciccone were the last survivors of a 14-man breakaway on the 160.5km stage from Mulhouse, and both received rich rewards at the top of a climb which left many riders struggling to stand at the summit.
Teuns could celebrate a first career Tour victory while Ciccone – a break-out star of the Giro d'Italia in May as he took a stage win and the mountains classification – did just enough to take the yellow jersey by six seconds.
"It is unbelievable," the Trek-Segafredo rider said. "This feeling is crazy. I am 24, I here for the experience and now I have the yellow jersey."
Deceuninck-Quick Step's Alaphilippe did not give up the jersey without a fight. Having stuck with the group of favourites all day, he attacked as the road turned to dust near the summit.
At first no one reacted, but Thomas then found the reserves he needed to spring past the Frenchman, who slumped on to the barriers as soon as he crossed the line.
The seconds Thomas has gained may not be massive – two on Thibaut Pinot, seven on Quintana and nine on a group including Jakob Fuglsang, Richie Porte and Bernal – but this was a clear answer to questions over his form.
Mitchelton-Scott's Adam Yates, a former resident of these parts, seemed to be caught out by the new finish as he finished 14 seconds behind Thomas, alongside UAE Team Emirates' Dan Martin.
"I feel really good," Martin said. "I lost a bit of time on the dirt section but I'm not worried. I think this Tour will be about who has the least bad day and today was definitely not a bad day for me."
It was, however, a bad day for French hope Romain Bardet, who faded on the steep finale and had the final indignity of dropping his chain on the line as he shipped almost three minutes. All French hopes have immediately shifted to the seventh-placed Pinot.
Thomas, sitting fifth, is now the best placed of the main contenders, four seconds ahead of Bernal in sixth and nine up on Pinot. The likes of Steven Kruijswijk, Rigoberto Uran, Jakob Fuglsang and Yates lurk, no more than 35 seconds back, but then more serious gaps open up.
In the Tour's previous three visits to this mountain the man in yellow at the summit would be wearing it in Paris come the final stage. All the signs on Thursday suggest this edition has more twists to come.
