Tour de France 2018: Geraint Thomas takes giant stride towards maiden yellow jersey as Chris Froome fades

Nairo Quintana won a thrilling stage on the brutal Col du Portet but Thomas's finish in third was the performance of a potential champion of the Tour de France

Any lingering doubts that Geraint Thomas cannot last the course to win a three-week grand tour were all but vanquished here on the brutally steep Col du Portet as the Welshman took a major step towards winning the Tour de France, resisting a wave of attacks to finish third and gain time on his rivals.

Tom Dumoulin came in five seconds later and he is now Thomas’s closest challenger after Chris Froome lost almost a minute in the final kilometre. Froome’s plans for a fifth yellow jersey may now have to be shelved to support his team-mate, with only two realistic opportunities for Thomas to be caught – Friday’s stage on the Col du Tourmalet and Saturday’s individual time trial when world champion Dumoulin will come to the fore – but the Dutch rider is 1min 59sec back and even he will not be able to close a gap that big over 31km.

Nairo Quintana won the stage with a perfectly measured assault, reeling in the solo break of Tanel Kangert, shaking off the attentions of Rafal Majka and withholding the gritty chase of Dan Martin, who finished second. It was Quintana’s first stage win of this Tour but with his deficit of more than four minutes at the start of the day, it was not enough to bring him back into overall contention.

The Portet took its toll, a climb where the legs burned, where a terrifying grimace contorted Martin’s face and a wash of sweat and saliva fell off Romain Bardet’s chin like a waterfall. At the front of it all was Quintana, crawling into the clouds with Martin in steady pursuit. A minute or so down the road were the rest of the leading contenders, where Thomas flung open his yellow jersey and set about putting out fires. Bardet attacked; Roglic tried to get away; Tom Dumoulin made a late burst; but each time Thomas held on.

Nairo Quintana won Stage 17 of the Tour (AFP/Getty Images)

Froome did not, however, unable to summon the kind of late surge that won him the Giro d’Italia, and it may be that ultimately trying to pull off the two races back to back was a step to far. There are still opportunities for him to claw back time, but this was not the look of Froome at his best and he admitted afterwards that he is now going only for a podium finish.

This uniquely short and strange stage 17 was always likely to prove crucial, although the cycling purists who dismissed the grid start as nothing more than a gimmick were quickly proved right: it had the look of a Formula One grand prix but not quite the explosive tension powering towards the first corner, as Geraint Thomas yawned off the start line like a man stirring from the sofa after a particularly long Netflix binge.

Tanel Kangert rides during a breakaway in the first pass of the 17th stage (AFP/Getty Images)

Kangert immediately took up the challenge powering to the top of the first of the day’s three gruelling climbs, Montée de Peyragudes, with a 20-second advantage over Tuesday’s stage winner Julian Alaphilippe and a couple of other chasers, with the Sky-led peloton three minutes down the mountain.

But Alaphilippe is a masterful descender – he showed as much on stage 16 when his chase pressured Adam Yates into a costly crash – and by the foot of the day’s middle climb, the Col de Val Louron-Azet, the Frenchman had reeled in Kangert. Together with Kristijan Durasek they formed a trio attempting to keep clear of a strong chasing group which included Yates as well as Majka, Bauka Mollema, and Alejandre Valverde.

Chris Froome fell away in the final kilometre (AFP/Getty Images)

Back in the peloton, which had shed the stragglers and shrunk to only 30 riders by halfway, an intriguing alliance of Bardet and Martin attacked with the help of their respective team-mates. Bardet’s lieutenant in the best young rider’s white jersey, Pierre Latour, took a huge self-sacrificing turn on the front but as ever Team Sky reacted quickly and efficiently to shut them down, the long white train in perfect mechanical order.

As they descended towards the start of the final climb, even the talented bike handling skills of Peter Sagan were feeling the strain, as he crashed and lost touch with the peloton, managing to eventually finish the stage. The gruelling Col du Portet then took its first victim on its Tour de France debut, when Alaphilippe took one look at the 16km haul to the top and sat up in his saddle, telling the cameras he was done. Suddenly Kangert was leading the race on his own, one monstrous climb separating the Estonian from his first Tour stage victory.

But Quintana brought him back, ditched Majka and powered on to victory. Behind him the peloton shed into a yellow-jersey group of nine, then five, then three, until only Thomas was left. He retains yellow, his lead increased, and looks every inch a grand tour winner in waiting.