L'Alpe d'Huez - Chris Froome said he felt like he was "dying a thousand deaths" on the final climb to Alpe d'Huez as he all but secured a second Tour de France victory on Saturday.
The 30-year-old Briton revealed he had been struggling with illness for a few days after holding off a stirring fightback by Nairo Quintana.
"I won't be lying if I say that there were a few moments when I thought: 'this will be tough here'," said the Team Sky leader.
"But we were getting time checks every few minutes and it was comforting to see the gap wasn't suddenly jumping up by 30 seconds; it was moving up by five or 10 seconds at a time so it was manageable.
"I was on my limits, it felt like I was dying a thousand deaths today but being with my teammates makes it a little bit more manageable and I had a little left to do that last kilometre and limit those losses."
Quintana had launched a last gasp attack on the 13.8km hors category and iconic climb to the finish of the 110.5km 20th stage from Modane.
And as he eked out an increasing gap to Froome, eating into the 2min 38sec deficit with which he'd started the day, the Briton admitted he was worried the Tour was getting away from him.
"It really was tough today but at the finish it was incredible, an incredible feeling and emotion," said Froome.
Frenchman Thibaut Pinot salvaged something from his disappointing Tour with victory on the penultimate stage but it was the battle between Froome and Quintana that really mattered.
Quintana finished second, 18sec behind Pinot, but Froome dug in to finish the stage fifth, just 1min 20sec behind Quintana.
The Colombian took six bonus seconds on the line but that still left him 1min 12sec short of overhauling Froome ahead of Sunday's final stage, which will culminate in Paris.
That gap was less than the minute-and-a-half Quintana had given up to Froome almost three weeks ago on the second stage when he was caught behind a crash in crosswinds.
"I gave everything right from the first week. We (Movistar) had some difficulties because we were caught up in a crash and I lost 1min 30sec - that's what lost me the Tour," said Quintana.
Just as in 2013, Froome, 30, has fought off an Alpine comeback from Quintana to beat the 25-year-old Movistar leader to Tour success.
His Sky manager Dave Brailsford told ITV4 that it had been closer than they expected.
"It was a bit close in the end. I think after everything he's endured, Chris has shown his real mettle," said Brailsford.
The final battle took place on the climb to the finish at Alpe d'Huez.
Sunday's final stage to Paris is nothing more than a procession and barring an unlikely crash, Froome will be crowned Tour champion.
But Quintana did not give up easily and first attacked on the hors category Col de la Croix de Fer some 60km from the finish.
Then again, right from the foot of the climb to Alpe d'Huez, Quintana launched the first of four attacks before finally getting away.
From there it was a race against time as Quintana tried to hunt down Pinot for the stage win, while also aiming to claw back his deficit to Froome for overall success.
By the end, though, Quintana had come up short on both counts.
"It was the last day and I had to try, I had to go for it," said Quintana.
"I thought we could get away on the Col de la Croix de Fer but it didn't work.
"I tried again on the final climb and got some time but it wasn't enough and I lost the Tour."
Froome said he expects Quintana to be back next year pushing him hard again.
"He's young, he's very strong and has a great mentality. He races hard, and at the right times," said Froome.
"He's got a great future and I think next year we'll come back to do battle again."