Chris Froome is closing in on a third Tour de France title after extending his lead in the yellow jersey while Russian Ilnur Zakarin won stage 17 to Finhaut-Emosson.
As Zakarin was celebrating his first Tour stage victory from the day's breakaway, Froome latched on to Richie Porte's late attack to ride clear of his rivals and build a cushion of almost two-and-a-half minutes.
Dutchman Bauke Mollema was the first to be distanced as his second place overall came under attack from Orica-BikeExchange's Adam Yates, but most encouraging for Team Sky will have been the sight of Nairo Quintana being unable to respond as others broke free.
The Movistar rider has usually come good in the third week of Grand Tours and threatened Froome's lead late in last year's Tour, but does not seem to have the legs to rival him and appeared to wave the white flag after dropping to three minutes 27 seconds off the pace in fourth place.
"I still have a lot of years," Quintana said. "I am 26, and there are a lot of people ahead of me who have more experience. I still have a lot of years ahead of me to fight for the 'yellow jersey dream'.
"I didn't have a great (day) today. I expected more because I had good sensations, but my body didn't feel good in the end. I did the best I could."
With this being Colombian National Day, the stage had been set for Quintana to show his colours, but he was visibly struggling as Froome and Porte rode away.
"It's been a very difficult Tour for Nairo," Froome said. "He's still a great rival and a big challenger for me but he lost more time today. I think for him to re-enter into the game again he's going to have to do a real good time trial tomorrow."
At the end of this 184.5km stage from Berne, Froome now leads Trek-Segafredo's Mollema by two minutes and 27 seconds after the Dutchman gave up 40 seconds on the climb to the Emosson Dam.
Third-placed Yates has seen his chances of a podium finish in Paris enhanced after the 23-year-old moved to within 26 seconds of Mollema and extended his advantage over Quintana to 34 seconds.
"I said if there's an opportunity to take some seconds I'd go for it," Yates said. "I'm satisfied with my performance. I took some time on Mollema but I wasn't thinking of Mollema himself, I was trying to bridge the gap to Froome and Porte."
It was here that Froome lost the race lead in the Criterium du Dauphine ahead of his ill-fated 2014 Tour, but there were no ghosts from that day on the spectacular hors categorie climb towards the snow line as Team Sky continued to offer the 2013 and 2015 Tour winner strong support.
He was guided up the final climb by team-mates Sergio Henao, Wout Poels and Mikel Nieve but after they had gradually peeled off, there was the familiar sight of Froome following Porte.
The Australian left Team Sky for BMC in the winter but did a super-domestique's turn in helping Froome distance his rivals while also moving himself up one spot to sixth overall.
"It did bring back a few memories," Froome said of attacking with his long-time training partner. "It was nice to ride with an old team-mate again but this time he was putting me under pressure, I was just staying on his wheel."
For Froome it was a near perfect scenario as he was pulled up the hill without needing to do a turn on the front himself ahead of Thursday's time trial.
"I don't think it was possible to go much faster there, Richie seemed to be doing just fine on his own," he said. "Tactically for me there is really no need to get on the front and start pulling on the final.
"Tomorrow is going to be crucial and this is the first day of a four-day block (in the Alps)."
Dan Martin attempted an attack on Froome during the closing five kilometres today before his challenge faded and he remains in ninth place in the general classifications.
Zakarin rode clear of stage 15 winner Jarlinson Pantano of IAM Cycling and Tinkoff's Rafal Majka on the last of the four categorised climbs to collect his first Tour de France stage win.
The Katusha rider was the only Russian to start the Tour, and his victory comes just two days after Richard McLaren's explosive report on state-directed cheating in the country.
Zakarin, who served a two-year doping ban after testing positive aged 19 in 2009, said he had not read the report as he focuses on the Tour.
"For me it is already quite a stressful time (being in the Tour)," he said as his team manager, Olympic triple gold medallist Viatcheslav Ekimov, translated. "I am not following the news."
Ekimov then added: "(Zakarin) is the most tested rider from Katusha, 12 times out of competition. All of the testing is performed in European labs, Lausanne, Paris, Barcelona.
"In Katusha we have our own anti-doping program, we have all the protocols. I cannot tell you how many times he has been tested inside the team but in every single race at least once he passed doping control."