At 2,304m altitude on the Tour's queen stage, the rarefied air and the ridiculously steep pitches sorted the pretenders from the major contenders.
And the man self-nicknamed Superman Lopez soared on a finish that was in no way his kryptonite.
"Well in truth we were confident," he said. "It was our terrain."
"Above 2000m is like being at home."
"We were waiting for a moment like today. We have been there and thereabouts with the fighting and we deserve it."
López' acceleration blew apart the main contenders behind including Colombian compatriot Rigoberto Urán who he leapfrogged in the standings to now sit fourth overall (+1:26), Urán slipping to sixth.
In the post stage interview, López was near to tears as he thought about the significance of his victory and his family.
"I'm super happy. Very emotional because we worked very hard. It hasn't been easy to get here.
"I think about my wife and my son. It's very hard to be apart from them. It's my job in the end. I do think about them all the time."
Roglič's lieutenant Sepp Kuss gapped the main contender bunch as he went in pursuit of López. But at the right time, he fell back to his leader and in a dip in the road, the Slovenian launched away, gapping Pogačar.
The yellow jersey crossed the line behind López, 15 seconds ahead of Pogačar and increased his lead over his compatriot to 57 seconds.
Another beneficiary of today's stage was Australian Richie Porte who moved to fourth from sixth as he gapped Enric Mas, Mikel Landa, Adam Yates and Rigoberto Urán on the climb. He now sits 1:39 off the podium.
Earlier on the stage, many riders tried but failed in cementing an early break. Thomas De Gendt (Lotto Soudal), one of the early protagonists attempting several attacks finally got away after 16kms quickly building a 16 second lead.
A big group of 20 riders pursued De Gendt launching themselves off the same uncategorised dig as the Belgian, reaching him a kilometre later.
As the race went up another uncategorised kick, Alaphilippe attacked that group pulling across Richard Carapaz (INEOS Grenadiers), Gorka Izagirre (Astana), Lennard Kämna and Dan Martin (Israel-Start-Up).
Jumbo-Visma started policing the front of the peloton expressing their satisifaction with the breakaway several kilometres later, the leaders' advantage swelling to over two minutes when they reached the intermediate sprint at the 45th kilometre.
Racing for 7th place through to 15th after Daryl Impey crossed over one minute behind the leaders in a desparate but soon abandoned attempt to bridge to the leaders, Michael Mørkøv piloted Bennett to the best of the rest of the points and increased his lead in green over Sagan to 47.
The leaders reached a maximum advantage of six minutes as they hit the Col de la Madeleine but it slowly tumbled to one minute and 40 seconds at the summit as Bahrain McLaren drove the pack hard, sensing a good day for their leader Mikel Landa which proved ultimately fruitless.
Richard Carapaz entered polka dot contention after crossing the KOM first but the new virtual leader at that stage was Pogačar as he led the peloton over the KOM to grab eight points. He would ultimately pull on the polka dot jersey after the stage.
Martin fell back to the main bunch after he was dropped on the descent and as the leaders hit the final climb, Alaphilippe tried his luck attacking Carapaz and Izagirre, but it was all for nought.
Carapaz upped the tempo 13kms from the top when the gap back to the peloton was down to a minute and it was enough to drop the Frenchman. Izagirre surrendered a few kilometres later as Carapaz held a slim 20 second lead over the bunch.
As the climb continued, the dynamic changes in the final six kilometres appeared to suit Carapaz and his lead increased to 40 seconds.
But his bid for stage glory was soon over.
The 2020 Tour de France continues with Stage 18, last drinks for the contenders before the final individual time trial. On this 167km Alpine stage, riders face 4,000m of vertical gain. Watch Stage 18 via the SBS ŠKODA Tour Tracker from 7:55pm (AEST) on Thursday, 8:05pm (AEST) on SBS On Demand, or tune into the television broadcast from 9:30pm (AEST) on SBS.