Wimbledon - 10hr match still not finished
The longest at Wimbledon was between Pancho Gonzales and Charlie Pasarell in 1969, which took five hours 12 minutes and finished 22-24 1-6 16-14 6-3 11-9 to Gonzales.
The scoreboard broke down, the umpire had to get down from his chair, stretch his legs and take a drink. His voice was almost hoarse. No-one had ever seen anything like it before.
The crowd's half-hearted Mexican wave could barely make it around Court 18 after an epic forever to be etched in the record books.
"Nothing like this will ever happen again. Ever," an exhausted Isner said, as the crowd, crammed into every nook and cranny around the court, chanted: "We want more, We want more."
It was a magnificent spectacle to watch - two players who absolutely, totally, utterly refused to give in.
At 59-59 in the fifth and final set, Isner was staggering around like a dazed fighter, Mahut flung himself across the court with breathtaking commitment.
Mahut, who had to survive the qualifying tournament just to reach the first round, had to serve to stay in the match 55 times before the Frenchman asked to stop.
"I want to play on, but I can't see the ball," he told the umpire, who eventually halted proceedings.
Mahut fended off two match points at 32-33, then survived another one at 58-59 when he fired down his jaw-dropping 94th ace.
Isner sent down 98 aces as both players eclipsed the previous record of 78 by Ivo Karlovic in a Davis Cup tie against the Czech Republic last year.
Former Wimbledon champion John McEnroe spoke for everyone privileged enough to watch the twilight marathon.
"This was the greatest advertisement we have ever had for our sport," he said.
It was Groundhog Day at Wimbledon. They finished all square on Tuesday night, they finished all square on Wednesday night. And after all that, it was still only a first-round contest.
The longest match in the history of tennis left the spectators gasping in awe - and it is still not over.
"Come on - one of you," shouted one exasperated wag as they battled each other to a standstill.
Fans crowded round every inch of the court, peering forward up to five deep. People stood on Henman Hill overlooking the court, even if they could only see one side of it.
The players were locked in combat but you could see the respect they had for each other. They even walked off court together for a toilet break as dusk gathered.
Angered at times by dubious linecalls, they were too tired to argue. Isner bit his shirt in frustration, Mahut thudded his racket on the grass.
When the players reached 50-49, the crowd rose to give them a standing ovation. Hands on knees, back bowed, Isner could barely stand.
The tennis world waxed lyrical about the epic twilight final between Roger Federer and Rafael Nadal two years ago.
The quality of tennis may not have reached such superb heights of artistry but, whatever the result on day three, the sheer guts and staggering stamina of Isner and Mahut will live long in the memory for everyone lucky enough to be there.
"I walked on court at about 11-all in the fifth and now I'm off and they're still going," Federer said after his second-round win against Ilija Bozoljac.
"This is absolutely amazing. In a way, I wish I was them, in some ways I wish I wasn't them. This is a very special match. I hope somehow this is going to end."
The winner of this clash will face Dutchman Thiemo de Bakker, who was also forced deep into a fifth set before beating Santiago Giraldo 6-7 6-4 6-3 5-7 16-14 in another match carried over from Tuesday.