Unsurprisingly Julian Alaphilippe (Quick-Step Floors) was also in close attendance, taking second place at the summit ahead of Kristijan Durasek (UAE Team Emirates) and Jesus Herrada (Cofidis), while a small group of chasers including Alejandro Valverde (Movistar) and Adam Yates (Mitchelton-Scott) formed behind.
Meanwhile all was calm in the GC group as Luke Rowe (Team Sky) set the tempo all the way up the climb, but there was a bit of drama for Nairo Quintana (Movistar) who suffered a puncture near the summit, requiring two stops - one for a new wheel and a second for a new bike - before working his way back in.
At the front of the race Alaphilippe, Kangert, and Durasek continued to tap away, holding a gap of around a minute over a chase group that was slimming by the metre, with Yates among those dropped by Valverde, Rafal Majka (Bora-Hansgrohe), Daniel Martinez (EF Education First-Drapac), Franco Pellizotti (Bahrain-Merida), and Omar Fraile (Movistar).
Having been dropped by Quintana, Majka was then caught and dropped by Dan Martin, but the Irishman was struggling to close the gap that had sat around 15 seconds for 10km, and the Colombian's acceleration opened the gap out to 30 seconds with five kilometres to go, before Martin once again began to claw him back.
Behind second place went to Martin who was still locked 28 seconds behind the Colombian, but there were movements from the group behind as Thomas attacked Dumoulin and Roglič with 300m remaining and immediately opened a gap.
That action means that Thomas now leads the Tour de France by 1-59 ahead of Dumoulin, with Froome at 2-31 and Roglič at 2-47. Quintana also moves up to fifth place at 3-30 thanks to his efforts.
How it happened
A large group formed within a few kilometres, before Tanel Kangert (Astana) attacked to ride tempo up the rest of the climb and take maximum points at the summit of the Montée de Peyragudes.
That means that while Thomas extended his lead at the top of the GC to 1-59, the man behind him is now Dumoulin while Froome drops back to third at 2-31 and now sits just 16 seconds ahead of Roglič .
Having descended to victory on Tuesday, Alaphilippe was clearly full of confidence on the descents and duly dropped Durasek as they dropped towards Loudenvielle, catching Kangert before the bottom.
With exactly three kilometres to go Roglič attacked and was immediately being followed straight away by Thomas and the rest of the contenders while Froome took a little longer to get back on.
Another attack followed from Roglič , and once again Geraint Thomas was able to follow while Dumoulin was distanced, but was once again able to work his way back up to Thomas and Roglič .
Soler led the GC group over the top, with four Team Sky riders including Thomas and Froome close to the front as the British team tried to take control of the rough and technical descent towards the base of the final climb.
At the base of the final climb with 16km to go, Alaphilippe and Kangert held a lead of 2-50 over the yellow jersey group, with the chasing group including Valverde having dropped back on the descent to 1-15.
That meant that the yellow jersey of Geraint Thomas was still back in the group, sitting on the wheel of Tom Dumoulin with the Dutchman forced to do the chasing of the two men sitting either side of him in the general classification.
Meanwhile as Poels pulled off the front of the yellow jersey group, Steven Kruijswijk (LottoNL-Jumbo) launched an acceleration, but just as was the case on Alpe d'Huez, Egan Bernal was setting a strong pace to keep the Dutchman in check.
Behind Bernal, Froome looked as if he was beginning to play games, once briefly accelerating up the side of the group to see if Dumoulin would follow, before dropping to the back with the Team Sunweb man still locked in his wheel.
And as soon as the peloton started to climb and Luke Rowe pulled off, Ag2r La Mondiale moved straight to the front and started riding hard with Silvan Dillier setting the pace ahead of Pierre Latour and, of course, Romain Bardet.
Dan Martin (UAE Team Emireats) was straight onto the wheel, but Team Sky looked non-plussed as Jonathan Castroviejo calmly closed the small gap that Latour had managed to open.
Tour de France 2018, stage 17: Bagnères-de-Luchon to Saint-Lary-Soulan Col du Portet, 65km
1. Geraint Thomas (GBr) Team Sky, in 70-34-11
2. Tom Dumoulin (Ned) Team Sunweb, at 1-59
3. Chris Froome (GBr) Team Sky, at 2-31
4. Primoz Roglic (Slo) LottoNL-Jumbo, at 2-47
5. Nairo Quintana (Col) Movistar, at 3-30
6. Steven Kruijswijk (Ned) LottoNL-Jumbo, at 4-19
7. Mikel Landa (Esp) Movistar, at 4-34
8. Romain Bardet (Fra) Ag2r La Mondiale, at 5-13
9. Daniel Martin (Irl) UAE Team Emirates, at 6-33
10. Jakob Fuglsang (Den) Astana , at 9-31
The 146 remaining riders of the 2018 Tour de France lined up in an innovative grid style start in Bagnères-de-Luchon, with the organisers hoping that someone would be willing to attack from the gun before the teams could get organised.
Dillier's pace-setting slimmed the group down considerably, and as soon as his work was down Latour accelerated hard to attempt to open a gap with Bardet locked in his wheel.
Crossing the line in third place not only gave him a gap of five seconds over Dumoulin, but also meant he took four bonus seconds. Meanwhile Froome was losing considerable time, and even lost the wheel of Bernal in the last few metres to finish 48 seconds down on Thomas.
Meanwhile Froome had to be paced through the final kilometres by the ever-impressive Egan Bernal, eventually crossing the line 48 seconds behind Thomas to drop to third in the general classification.
The yellow jersey group crossed the top of the climb 3-30 behind Kangert at the front of the race, with the Valverde group roughly midway in between the two.
As soon as the GC contenders hit the climb Marc Soler stamped on the pedals to move off the front, with Jonathan Castroviejo (Team Sky) tracking his compatriot. Realising that Castroviejo was there, Soler sat up before Martin attacked in a move that was followed by Nairo Quintana (Movistar).
However at the front of the race victory was going to go to Nairo Quintana (Movistar), who took his second Tour de France stage victory and his first since his maiden Tour in 2013.
General classification after stage 17
Nairo Quintana (Movistar) took victory on the 65km stage 17 of the 2018 Tour de France, on a day where Geraint Thomas (Team Sky) extended his lead at the top of the general classification and team-mate Chris Froome was dropped.
The Colombian attacked at the base of the finishing climb, and held off a dogged pursuit by Dan Martin (UAE Team Emirates) up the Col de Portet to win his first Tour de France stage since 2013.
Meanwhile there was drama in the main GC group as attacks by Primož Roglič (LottoNL-Jumbo) and Tom Dumoulin (Team Sunweb) saw Chris Froome dropped in the final three kilometres of the climb.
Dumoulin took his time, but steadily worked his way back up to Roglič and Thomas over the next kilometre. Meanwhile Quintana had worked his way up to Valverde, with the Spaniard going into domestique mode and setting the pace for Quintana around 1-30 behind race leader Kangert who was still doing a sterling job in the lead further up the mountain.
That sign of weakness encouraged Dumoulin, who took a few hundred metres to catch his breath before launching an acceleration of his own which was followed by Thomas, Roglič , and Kruijswijk, while Froome relied on the pace-setting of Bernal to help him limit his losses.
However the yellow jersey of Thomas was in no such trouble as he followed the attacks before sprinting away in the final 300m to take third place on the day, which included the four bonus seconds, and open a gap of five seconds back to Tom Dumoulin.
With 200m to the summit Alaphilippe accelerated for the points with Fraile in his wheel to take maximum points, while Durasek was distanced and was unable to get back on down the descent.
Looking far better than he had in the Alps, Quintana eased into a 30-second lead ahead of the yellow jersey group, picking up riders from the early breakaway one by one as he made his way up the mountain.
The next attack from the lead group was a more threatening one as Primož Roglič (LottoNL-Jumbo) a strong time triallist sitting at 2-38 accelerated away, and was immediately followed by Chris Froome.
Back in the yellow jersey group and Egan Bernal was briefly the only domestique alongside Froome and Thomas, before Wout Poels recovered to move to the front and set about controlling the gap to Quintana.
However the Colombian was looking strong as he dropped Valverde and plugged away with Majka in his wheel to extend his lead over the GC group to a minute with nine kilometres to go and catch Kangert shortly after.
1. Nairo Quintana (Col) Movistar, in 2-21-27
2. Daniel Martin (Irl) UAE Team Emirates, at 28 secs
3. Geraint Thomas (GBr) Team Sky, at 47 secs
4. Primož Roglič (Slo) LottoNL-Jumbo, at 52 secs
5. Tom Dumoulin (Ned) Team Sunweb, at same time
6. Steven Kruijswijk (Ned) LottoNL-Jumbo, at 1-05
7. Egan Bernal (Col) Team Sky, at 1-33
8. Chris Froome (GBr) Team Sky, at 1-35
9. Mikel Landa (Esp) Movistar, at same time
10. Ilnur Zakarin (Rus) Katusha-Alpecin, at 2-01
The good news for Latour was that his acceleration did see white jersey rival Guillaume Martin (Wanty-Groupe Gobert) dropped, but most of the GC contenders looked comfortable in the wheels.
However as soon as the road ramped up Kangert was off, with Alaphilippe calling it a day having picked up plenty more mountains points on the day to tighten his grip on the polka dot jersey.
Despite being the man that launched the attack, Martin was unable to stick to Quintana's wheel, while Castroviejo resumed his position at the front of the group of GC contenders and showed no urgency in chasing down Quintana who started the day 4-23 behind the yellow jersey of Thomas.
Wout Poels continued to lead the yellow jersey group as the gap remained locked at around a minute, setting a pace that saw Romain Bardet dropped, before Quintana attacked Majka with 6.4km to go as he went in search of a stage victory and a move up the general classification.
Unfortunately, that didn't happen, as the GC contenders looked more than happy to wait for their domestiques to get to the front as various non-threatening attacks went off the front in the opening couple of kilometres.
The Col de Val Louron-Azet started rudely with a 10 per cent with Alaphilippe, Kangert, and Durasek holding a 1-15 gap over the chase group, while the peloton started at around 3-20.
One of the men who had dropped back from the break was Marc Soler (Movistar), who then took over the work on the front of the yellow jersey group to drop Latour, while Kwiatkowski moved up into Soler's wheel with Thomas and Mikel Landa (Movistar) making sure to be close to the front.
Tom Dumoulin will miss Tour de France as Jonas Vingegaard named as replacement
There had been rumours of a comeback in time for the Tour
By Jonny Long •
Primož Roglič won't race either the Dauphiné or Tour de Suisse in build-up to Tour de France 2021
Liège-Bastogne-Liège will be the Slovenian's last race for two months before the start of the French Grand Tour
By Jonny Long •
Sir Bradley Wiggins still believes Chris Froome can win another Tour de France
Sir Bradley Wiggins still believes Chris Froome can win a fifth Tour de France title.
By Alex Ballinger •
Don't expect a normal Tour de France this year, UCI warns
The UCI's medical boss has reiterated that living with the virus for years to come will also impact the future of the world's biggest bike race
By Jonny Long •
'They trust me a lot, to lead the team is a great challenge' says Richard Carapaz on Tour de France ambitions
The Ecuadorian has set himself some big goals for the 2021 season
By Tim Bonville-Ginn •
Marcel Kittel reveals the power numbers and effort behind his most successful Tour de France years
Marcel Kittel has revealed some of the staggering power numbers behind his most successful Tour de France years in a new study.
By Alex Ballinger •
Tadej Pogačar will defend title at Tour de France 2021 before taking on Vuelta a España
Marc Hirschi will also represent UAE Team Emirates at this year's French Grand Tour
By Jonny Long •
Thibaut Pinot will not ride the 2021 Tour de France, according to reports
Instead, French media sources indicate Pinot will turn to the Giro d'Italia
By Jonny Long •