After days of riding conservatively, Yates threw caution to the wind on stage 19 and opted for an all-out move 10 kilometres from the line at the summit finish of La Rabassa in the Pyrenees.
He finished second on the day to stage winner Thibaut Pinot (Groupama-FDJ), but Yates’ aggressive style reaped rich rewards, as GC runner-up Alejandro Valverde (Movistar) struggled and the Briton's advantage tripled on the overall. Yates' lead went from 25 seconds to 1:33 over Valverde. Enric Mas (Quick-Step Floors), previously third overall, also was unable to respond and got bumped down to fourth by Steven Kruijswijk (LottoNL-Jumbo).
As he has done ever since he took the lead, Yates continued to warn that anything can happen in the final two days. But with his GC advantage over a minute for the first time in the race, his first Grand Tour victory looks all but certain.
Yates explained that he had switched to a much more aggressive way of racing rather than simply trying to defend.
“When I try and defend the jersey it never seems to go to plan, so I tried to be more aggressive, and that's the way I like to race, so I'll continue to do that," he said.
"There were a few guys ahead, and it felt like a really good moment to go across to those guys," he said, referring to a move up the road that included Pinot, Kruijswijk, Nairo Quintana (Movistar) and George Bennett (Lotto-JumboNL. "And that was it really, from there a bloc to the finish."
There was indeed more than an air of liberation about the way Yates, free of his more conservative earlier strategy, let rip at the front of the little breakaway. The Briton was hammering so hard on the pedals that riders like Kruijswijk looked to be hanging on for dear life at times, and Quintana was also dangling off the back.
The Colombian, who had another difficult day, suffered a mechanical when he dropped back to help Valverde, whilst Yates blasted on regardless. Only Pinot looked able to give the overall leader much of a hand in opening the gap, and the Frenchman was the only rider able to stay with Yates then break away at the finish.
Second on the line, with a 1:38 advantage overall and in a class of his own on this first of the two high-mountain stages in the Pyrenees, Yates continued to preach caution about his chances of victory. Asked what percentage of the win he felt he had in his pocket, Yates said, "None, because the race doesn't finish until tomorrow [Saturday]. I have to be careful. It's going to be a very difficult day."
The events of the last weekend of the Giro d'Italia in May, it seems, have not yet been forgotten because of one impressive performance in the mountains, as Yates said.
"I know well how everything can change in one day - race doesn't finish until Madrid," he cautioned. "The team really supported me, and I hope we can stay focused, because [Saturday] will be a really hard day. Anything can happen. We should be ready for anything, and we should take it from there."
Asked if the overall win would represent the confirmation of his ability in the three-week stage races, Yates said, "I feel I already arrived in the Grand Tours in the Vuelta 2016, when I finished sixth. Then I got seventh in the Tour de France, the Best Young Rider's award in 2017. I've always been there or thereabouts, slowly improving."
But for all his aggressive performance on Friday, Yates insisted, once again, on playing it cool concerning his overall chances.
"Tomorrow is a difficult day, anything can happen," he warned. "We have to keep our feet on the ground."
Perhaps so, but on Friday, in cycling terms at least, Simon Yates was flying.