We saw gridlock at the start of stage 17 but by the time the GC contenders crossed the line atop the Col du Portet, after 65km of racing in the Pyrenees, the 2018 Tour de France was provided with the clearest snapshot yet as to how the race will end in Paris.
Nairo Quintana finally built upon the groundwork laid by his Movistar team in the early phases of the race to keep his hopes of finishing on the podium alive, but the true victor on Wednesday's summit was Geraint Thomas, who not only displaced Chris Froome as Team Sky's leader but did so without fuss or fracas.
That Froome could not hold the pace with 2.4km remaining finally ended the debate over leadership. Froome's hopes of a fifth Tour de France victory faded into the mist of the Pyrenean mountainside.
Thomas now leads primary threat Tom Dumoulin, who also lost a handful of seconds to the Welshman, by 1:59, while Froome has slipped to third overall at 2:31. We may not have seen the seismic shift in GC that was predicted on the eve of the stage but perhaps those kind of days are long gone. Thomas has instead built his lead on two factors: a mistake free opening nine days, followed by a flawless second half in which he has been equal to, if not better than, his pure climber rivals.
Thomas is now the favourite to take the yellow jersey all the way to Paris, having backed up each performance in the Tour mountains with a series of measured and mature rides. That his only significant acceleration came when the line was in sight and helped gain him an extra few seconds will be all Team Sky need to assure themselves that the yellow jersey is on the shoulders of their strongest rider. Until this point their dominance - despite the expulsion of Gianni Moscon and the unsavoury comments from their manager about the home nation - has been absolute.
Froome's slip to third overall may not matter if Thomas remains in control but the deficit to Dumoulin will concern the number-crunching boffins at Team Sky HQ. The Dutchman is the superior time trialist, and the nightmare scenario for Team Sky would be for Thomas to crack towards the end of the final mountain stage and for the defending champion to have already run out of terrain on which to test his Giro d'Italia rival.
However, that scenario would involve Froome recovering from this performance, which is the first time he has been thoroughly outclassed by a Team Sky teammate in the Tour de France mountains since his stunning emergence as a GC rider in late 2011.
Thomas' race to lose
Yet this Tour de France is not over, and the door is ajar just enough for a slimline Roglic to slip through or a brawling Dumoulin to burst it open.
Thomas, for all his talent and consistency cannot yet be considered a Tour de France closer. A victory at the Criterium du Dauphine or Paris-Nice is not the same as three-week racing, and there is still enough terrain between now and Paris for cracks to emerge and for rivals to exploit.
The race heads to Pau on stage 18 but Friday's stage delves deep into the Pyrenees for yet another series of mountains. The following stage is a gruelling individual time trial in the hills of the French Basque Country and the doubts about Thomas may only intensify as he draws closer to victory. What we know after Wednesday's stage is that the Welshman is the favourite and this is his Tour de France to lose.
As for the rest of the GC battle, LottoNL-Jumbo have continued to impress with a blend of free-flowing attacking and a maturity that also knows when it is better to defend. Both Steven Kruijswijk and Primoz Roglic have played cameos based on far more than token heroism in this year's race and have formed a double act that has tested their rivals throughout.
Their enemies haven't known which rider to mark more closely. Although Roglic sits higher up on GC, it was he who launched the first attack from the Dutch team on the final climb on Wednesday. Kruijswijk chipped in with his own series of short surges but Roglic's first assault, which drew a response from Froome was surely one of the factors that caught up with the British rider towards the summit. The Slovenian rider is now just 16 seconds off Froome's third place and breathing down the Giro winner's neck.
The stage's ultimate loser outside of Froome was Romain Bardet, who was unable to hold the wheels and lost contact several kilometres from the summit. Where exactly Bardet's GC race ended is unclear. Was it during the first half of the Tour when his main weapon - his AG2R La Mondiale team - were decimated, or perhaps on the second rest-day when he threw in the towel and told the media that winning this year was beyond him. On the final climb he looked isolated, his face desolate, as if he knew his fate. It's over for this year and even a stage win looks unlikely.
Dan Martin swam through the channels between Quintana and Froome and claimed a valiant second place on the stage to the summit of the Col du Portet.
He always gives the impression that he needs to do an awful lot of work for just a few seconds rewards but it was the Irishman who broke the deadlock in the GC group before Quintana launched his winning attack. Martin sits in ninth, too far back to realistically penetrate the top five, but a second stage win in this race, is not out of the question. This Tour may appear over to some but there's still life in the 2018 edition.