The breaststroke gold was his third at the La Defense Arena but the 22-year-old has rewrote the script on what was previously thought possible by becoming the first to medal in both of the demanding disciplines.

Even U.S. great Michael Phelps, whose coach now works with the Frenchman, did not achieve that.

With the crowd chanting his name at every stroke – “Leon, Leon” echoing around the arena – Marchand led every metre of the breaststroke before touching out in two minutes 05.85 seconds.

The world record, set by China’s Qin Haiyang last year, stands at 2 minutes 5.48 seconds and Marchand was set to beat that up to the 150m mark.

Australia’s Zac Stubblety-Cook, the 2021 champion in Tokyo, had to settle for silver while Caspar Corbeau of the Netherlands took the bronze.

Marchand, who won the Individual Medley on Sunday, sent sound levels off the scale from the moment he stepped onto the pool deck.

In the butterfly race he beat Hungary’s world record holder and reigning champion Kristof Milak into second place, with Canada’s Ilya Kharun finishing third.

Unlike in the later breaststroke, Marchand was behind until the final length when he overpowered Milak and surged past to win.

He returned for the podium ceremony, saluting the cheering crowd as the “Marseillaise” national anthem sounded, and then made a quick exit to prepare for the breaststroke.

Such was the sense of anticipation ahead of the later event that the poolside volunteers removing the athletes’ clothing boxes left more hurriedly than usual, sprinting even, to catch the race on television.

All over town crowds waited and watched as history unfolded, spectators at the table tennis venue singing the anthem after Marchand’s first gold of the night.

To win both titles was a simply astonishing achievement. To do it at a single Games even more remarkable. To take double gold on the same night, with a medal ceremony in between, truly the stuff of fiction.