While he seized the moment to attack the main protagonists in the mountains, his courageous ride is only likely to have extended his stay in yellow for 24 hours, as the Tour continues with another day for the climbers on Wednesday.
Team leader Adam Yates managed to stay out of trouble and finish in the main peloton with Chris Froome and is now sitting ninth overall only one spot behind Froome and on the same time.
General Classification 1. Greg Van Avermaet (BMC Racing) 40:34:28 2.
"Obviously I'm devastated", said Porte. Second place went to the Colombian Fernando Abra (Quick-Step Floors), the third Slovak Peter Saan (Bora-Hansgrohe).
Sunday's course will include some cobbled sectors used in the single-day Paris-Roubaix race.
AG2R La Mondiale's Romain Bardet had three punctures, including one with just 6km to go, but chased back on each time, despite Froome putting in a brief dig at the front late on in an apparent attempt to distance the Frenchman, who lost just seven seconds on the line.
Digging deep within himself Bardet however somehow made it back to the Froome group shortly before the finish line after a huge effort that saw the French hope gasping for breath. Three years ago he showed his calibre on these roads with victory in Paris-Roubaix, just a month after he won Milan-Sanremo.
"What can you do?" he said.
As Movistar veteran Alejandro Valverde puts it, "You can't win the Tour on the cobbles, but you sure can lose it".
"A lot of people didn't believe in me anymore and thought I wouldn't come back to the same level".
The route starting in Arras contained the highest number of cobblestone sections since the 1980 Tour, with almost 22 kilometers altogether.
Lotto-NL Jumbo's Dylan Groenewegen comprehensively proved that the new has well and truly eclipsed the old as the precocious Dutch powerhouse cruised past the best sprinters in the world to take stage eight of the Tour de France in Amiens.
After the first rest day Monday, the Tour resumes in the Alps on Tuesday with a 158.5-kilometer (98.5-mile) leg from Annecy to Le Grand-Bornand featuring four serious climbs.