Chris Froome has revealed that he played a high-risk game of brinksmanship on a Pyrenean stage of the Tour de France when he hit the wall on the climb to Peyragudes on an afternoon that he says could have been “a catastrophe” for his hopes of a fourth victory in the race.

Froome’s Team Sky colleagues were in their familiar position at the front of the peloton as the race headed up the Col de Peyresourde, but as Michal Kwiatkowski finished his turn around 7 kilometres from the finish, Froome suddenly ran out of energy.

By the end of the stage he would lose the yellow jersey to Astana’s Fabio Aru, with AG2R-La Mondiale rider Romain Bardet winning on a day when the closing few hundred metres were played out on a 20 per cent ramp.

But he has now revealed in an interview with Sunday Times sports writer David Walsh that the bonk he hit that afternoon could have cost him the overall victory.

“It was a disappointment that could so easily have been a catastrophe,” he said of the 12th stage of the race from Pau.

Following the stage, Froome admitted that he “just didn’t have the legs on the final kick,” but he has now revealed just how tough the day was, and how he employed a bluffing strategy any top poker player would have been proud of to conceal his weakness from his rivals.

Recalling how his Team Sky colleagues paced him towards the final climb, he said: “I’d feel the extra ache and get on the radio to encourage them, ‘You’re doing a great job. This lead group is getting a lot smaller. Keep it going.’ They were doing a lot of damage and I felt fine.”

But, with 4 kilometres remaining of the climb of the Peyresourde, after which there were still 3 kilometres to the finish, he ran out of energy.

Froome said: “It just felt like a switch had been flicked. From feeling good, I was suddenly empty. I felt lightheaded and weak, really weak in the legs. Every pedal stroke hurt.”

By now, it was Mikel Nieve who was setting the pace in the group, and Froome said he will “always remember the look” the Basque rider gave him when he asked him to ease off, which he described as “half kind of, ‘Did you just say slow down?’ and half fear.

“We’d pushed it so hard all day and then for me to ask them to slow down was quite a shock to Nieve. Once you run out of fuel there’s nothing you can do to bring yourself back.”

He continued: “I tried to make it look like I was OK when in fact the truth is that I was really terrible on the last kilometres of the Peyresourde.

“If you look at the footage you will see I was out of the saddle quite a bit. I was looking into the faces of each of my rivals, trying to read them.

“They were thinking, ‘Chris is trying to read me because he wants to attack, he’s ready to go’.

“By the time we get to the last kilometre of the Peyresourde I pulled off Mikel Landa’s wheel, went to the side, looked back, giving the impression that I had lots of energy.

“If anyone had attacked I wouldn’t have tried to go after them, just gone into time trial mode to get to the finish as efficiently as possible.”

His experience that afternoon gives an insight into the demands of a Grand Tour, because he believes the problem wasn’t due to anything that happened on the stage in question, but rather during the preceding days – ones that might be assumed as being routine for the overall contenders.

“There was no question in my mind about what happened. The legs felt good, the power was there but I had a fuelling problem. My mistake wasn’t on that day but in the build-up to it.

“We’d done two flat stages before Peyragudes and I’d eaten less than I should have. That had a knock-on effect even though on the mountain day itself I ate plenty.

“You learn lessons in every Tour and that was an important one for me. From Peyragudes to Paris I didn’t stop eating and ended weighing almost 1.5kg more than I’d been at the start of the race.”

He also praised the Polish former world champion Michal Kwiatkowski for his efforts during the Tour.

“Michal is such a versatile rider, able to win one-day classics, one-week stage races and become world champion at 24,” he said.

“His attitude is incredible, on and off the bike he is a pleasure to be around.

“If we’re talking about people who have made sacrifices to put me and keep me in the Yellow Jersey he would have to be the number one.

“If he’d been in any other team, he would have been going for the podium and if not that, a handful of stage victories.”

Froome is now heading to the Alps for a two-week training camp ahead of the Vuelta a Espana, a race in which he has been runner-up on three occasions.

He is seeking to be just the third man in history to win the Tour de France and the Vuelta in the same season, and the first since the Spanish Grand Tour moved from its former slot in the springtime.

“Previous years, the Vuelta felt like an afterthought,” he added.

“This year we’ve thought about it a lot. We’re going there with a sense of mission and I just want to have a real shot at it.”