There was some conjecture that the attacks from the big-name riders would come from the start of the race, but it was only 11th-placed Alejandro Valverde (Movistar) out of the pre-race big names who opted to go with the early move. As the Spaniard was nine minutes and thirty-six seconds down at the start of the stage, he was allowed some leeway to get up the road.
The early climbs were hard affairs, with the early breakaway splitting apart due to attacks at the front, while the peloton inexorably ground their way closer.
The unrelenting final climb of the Col du Portet proved to be the unravelling of the peloton, leaving the main contenders for the general classification to fight it out for the stage victory and a potential yellow jersey in Paris.
Dan Martin (UAE Team Emirates) was the first to hit out with 14 kilometres remaining, with Nairo Quintana (Movistar) jumping on the Irishman's wheel to follow. Martin and Quintana were also down on the general classification and provoked no immediate response from Team Sky, whose normally impressive armada was reduced to just a select supporting cast for Geraint Thomas and Chris Froome.
Quintana rolled over the top of Martin and started setting a higher pace, setting off up the road to join teammate Valverde, who helped pace the Colombian for a few kilometres before Quintana was again on his own.
Behind, there was a big attack from the peloton with Primoz Roglic (LottoNL-Jumbo) surging clear of the group, with Froome immediately jumping on the dangerous Slovenian's wheel. He stayed stuck to Roglic's wheel, while Tom Dumoulin led the group behind, meaning that Team Sky were sitting pretty while their two main rivals for the yellow jersey were doing the work.
The pace of Dumoulin was enough to bring Roglic and Froome back into the fold, as Quintana swept the remnants of the breakaway to take the lead on the road.
A series of attacks in the final kilometres saw Froome falter and drop behind, with an acceleration from Tom Dumoulin proving the final straw as the Dutchman was followed by Roglic and Thomas to form the final elite selection that would battle it out to the line.
Egan Bernal was left to pace Froome, and was often seen looking over his shoulder to make sure he didn't leave his team leader.
Thomas emerged the strongest, jumping clear in the final few hundred metres to take third on the stage behind the strong rides of Quintana and Martin.
Geraint Thomas (Team Sky) - 1st overall - Leads race by one minute 59 seconds
When asked by Cycling Central reporter Sophie Smith after the stage 'Is it possible that he'll back you now for the rest of the race?' Thomas responded, "
"I think I'm in the best position now, obviously. I think the whole team, we just need to keep doing what we're doing. I'm feeling good, I just need to keep recovering now, keep eating and doing all the small things right."
"It was a fast day. Luckily we controlled the start really well, the first climb wasn't too full gas but the second climb was hard, as was the last climb from the bottom."
"But it was a big,big day, happy to get through and extend my lead actually over Dumoulin."
Tom Dumoulin (Team Sunweb) - 2nd overall - One minute and 59 seconds behind Thomas, 32 seconds ahead of Froome
The big Dutchman has moved ahead of one Team Sky rider, but still has an almighty gap to close down between himself and Thomas.
"This was all I had," said Dumoulin. "Thomas was slightly stronger than I was and I have to deal with that."
"The first attempt of Roglic in the final, I saw that Froome was in difficulty but I didn't know if it was bluff or not. I waited a liitle bit then with my own attack - I went, I tried. I didn't have the legs to drop Thomas and Roglic. In the end I was happy to stay with Roglic, Thomas was just the strongest."
Primoz Roglic (LottoNL-Jumbo) - 4th overall - 16 seconds behind Froome, leads Quintana by 43 seconds
The former ski-jumper was in fine form on the final climb, attacking a number of times and was able to help Dumoulin drive up the advantage over Froome. Roglic was asked whether he was surprised that Froome had shown some weakness on the final climb.
"Well, surprised? We are all humans in the end and you just need to fight every day," said Roglic.
When queried over whether he had his eyes on a podium spot in Paris, Roglic replied.
"I don't bother myself with these places or seconds or whatever. I need to focus on myself, because it's ok tomorrow but still a really hard day in the mountains and the time trial so a lot, a lot of things can still happen."
"My goal... you always want more and more and more. But still it's the second Tour de France in my life and the third grand tour in my life. Maybe, maybe, but you need to be realistic - just race and go day by day."
Nairo Quintana (Movistar) - 5th overall - 43 seconds behind Roglic and 49 seconds in front of Steven Kruijswijk
“It was a really hard day, but a magnificent one for us, really comforting," said Quintana. "It was a stage I had marked down many weeks before this race, one I had prepared well for. I regret so much not having found good legs prior to this stage; my body just didn’t feel right, and lost too much time, which made me feel bad.
"Fortunately, I’m doing well now – let’s hope we can take advantage and fight hard on Friday, because we really believe we can still do something big in this Tour. The Movistar Team always trusted my skills – and here are some results to pay them back them!"
Quintana is currently three and a half minutes behind Thomas in the battle for the yellow jersey and it would take a truly spectacular performance for the pint-sized Colombian to wrest the lead away from the Welshman.
“The team was perfect today," said Quintana. "We had Alejandro up there in the breakaway, helping me out as much as he could after the attack I had launched. Also Soler, leading the peloton with a hard pace, trying to make things harder for our rivals before my move.
"We knew it was a finish for pure climbers, and it showed today. Thanks to the team’s work and Alejandro’s support, I could ride over the Col du Portet as if it were a mountain TT, and attack without looking back.
"This win gives me massive confidence for the remainder of the Tour de France. We must continue fighting and attacking – we know the GC win will be extremely hard, but we’ll try to make the race hard and see how far we can reach."
Romain Bardet (AG2R La Mondiale) - 8th overall - 39 seconds behind Mikel Landa, one minute and twenty seconds ahead of Martin
A poor day for the great French hope, he dropped off the pace of the main contenders with five kilometres left in the race and had to grind his way to the finish to limit his losses.
"It was a terrible day where my legs just did not respond," said Bardet" It’s unfortunate, but sometimes that’s how it is. This is sport, and you have to accept it.
"It did my maximum, but I was just the victim of terrible legs at the end. I actually had good legs through most of the stage, but on the last climb, I just could only climb at my pace. And that was really not good. I couldn’t accelerate anymore.”
Dan Martin (UAE Team Emirates) - 9th overall - one minute and twenty seconds behind Bardet, three minutes ahead of Jakob Fuglsang
Martin was stuck in no man's land on the final climb, always in between groups after being left behind by Quintana early. He finished second, a very strong performance given that he held off the rest of the bunch going at near full pace.
"The last two or three days have felt really good," said Martin. "It's a really good sign I kind of planned to go earlier, that's why we put Darwin (Atapuma) in the break. It's ok everyone saying 'attack early' but there was so much wind on those early and you get so much help being on the wheel that it's just not worth it."
"I had confidence in my legs and felt that I could do a good last climb. I attacked and Nairo came with me and attacked me straight away... he didn't really attack me, I think he wanted to ride together. He just rode so hard at the bottom that I wanted to set my own tempo. I turned it into a time trial to the top. Those last two (kilometres) got me - it's pretty high up here."
"I'm really proud of the way the team rode and how I rode as well. It's pretty special to get second on a mountain-top finish especially where it was a situation where the strongest got first. To be the second strongest on the hardest mountain-top finish of the Tour de France is pretty special."
Stage 18 is a much more sedate profile than the past few stages, with a sprint finish or breakaway likely to be the result in Pau.
