But when the Colombian first heard he was in yellow, halfway down the Col de l'Iseran after the race organisers decided to halt stage 19, he refused to believe it.
"It was all so strange, stopping the stage like that, that when I was in the team car and they told me that I was the leader, it just didn't make sense," he said afterwards. "It was only when I was on the podium putting on the yellow jersey that it finally began to sink in and I really believed it."
That was far from being the only moment when Bernal refused to believe his ears on Friday's stage, given when he heard that they wanted to neutralise the stage, he felt it did not make sense either.
"I heard, 'Stop, stop,' from the organisers and I didn't believe it, and I just kept going. I said, 'Not now, not now.' I didn’t know what the results would be.
"Then the team told me over the race radio the race was annulled. I told them to tell me in Spanish to be completely sure."
Then, and only then, after hearing the same words in his own language did Bernal opt to stop. It must have felt wholly surreal. But the sense of being in another world probably didn’t end there, given that 90 minutes later he was kissing his girlfriend at the foot of the winner’s podium, en route to becoming Colombia’s first yellow jersey wearer since Fernando Gaviria last year - but likely its first ever winner outright.
The consequences of such a victory - assuming there is no last-minute disaster - would be massive for the South American nation, as well as giving Sky/Ineos their fourth winner and seventh Tour triumph in eight years.
As for the question marks over what could have happened at Tignes, they will always, now, remain in the area of complete, and ultimately futile, speculation.
Once he knew what was going on, Bernal supported the decision to halt the race, saying, "We realised that the stage could not continue under these circumstances. It was the best place to stop everybody."
In terms of the tactics, and asked why he had opted to attack from a long way out on the Iseran - or what would have been had the Tignes climb not been cancelled - Bernal argued: "It was a difficult decision. If I lost my podium position because I cracked, there would be other years. I'm only 22. But if I won, then I could have been fighting for the Tour. And if I hadn't done it, there'd always be a nagging thought at the back of my mind, wondering what might have happened."
As for how he will now tackle the Tour from this point, on the final climbing stage to Val Thorens, Bernal argued: "The most logical thing would be to defend my lead. We're in a good position, and I have a very strong team."
Should Bernal take the yellow into Paris, at 22, he will become the youngest post-war Tour de France winner, with the final part of the puzzle falling into place thanks to a dramatic mountain-top attack. But whilst hoping there would be more attacks of that kind in the future in the sport, Bernal said he had no intention of changing his attitude to racing as a result.
"I'd like that. I hope so. But I want to go on doing what I've been doing up to now, enjoying racing and with that adrenaline you get every time at a race. I don't want to think too hard about the future and just enjoy my racing for now."
Looking remarkably poised for somebody who is leading the world's biggest bike race in what is his only his second-ever Grand Tour, Bernal only looked momentarily confused when somebody asked him what would happen if Thomas decided to fight for his own chances on the final mountain stage.
Bernal said he would respect his decision, although he didn't think it would make sense, nor that it would actually happen - something that Thomas later effectively confirmed by saying he will go all out to support his Colombian teammate.
Asked if he could really believe he was in the race lead, Bernal answered simply: "No. You tell yourself it might happen, like anybody would like to do when they're young and dreaming, but in my heart of hearts, I did not. You think it's almost impossible."
But it is a reality, now, and come Sunday, the path to overall victory is all but clear. And he will surely believe it 100 per cent by then, too.
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Alasdair Fotheringham has been reporting on cycling since 1991. He has covered every Tour de France since 1992 bar one, as well as numerous other bike races of all shapes and sizes, ranging from the Olympic Games in 2008 to the now sadly defunct Subida a Urkiola hill climb in Spain. As well as working for Cyclingnews, he has also written for The Independent, The Guardian, ProCycling, The Express and Reuters.