The finish at the summit of the Col d’Izoard will provide another reshuffle, probably a more meaningful one, but over another great ascent, the Galibier, the first Alpine stage provided more than a few hints of what may be seen amidst the Death Valley decor of the Casse Deserte. The Slovenian time triallist Primoz Roglic was a worthy winner at the expense of Alberto Contador, but they were essentially the warm-up act.

With the help of his team-mate Mikel Landa, Chris Froome brushed aside attacks from Romain Bardet and Daniel Martin to retain the yellow jersey, gaining ground on all his rivals apart from Rigoberto Urán, while Fabio Aru looks to be running out of steam and Simon Yates’s grip on the white jersey is far from secure.

With its bleak screes and vermicelli hairpins, the Galibier is perhaps the most daunting Alpine climb tackled regularly by the Tour, lacking only a few sun‑bleached bones to make it the perfect picture of desolation. But the time gaps that may prove critical by the weekend were opened on the descent, on the more straightforward high-speed road down from the Col du Lautaret into the finish.

Tour de France: Primoz Roglic wins stage 17 as Froome extends lead – live! Read more

The final five kilometres to the summit high above the village of Valloire were punctuated by attacks from Martin and Bardet, who repeatedly attempted to put Froome under pressure. Landa looks as if he has yet to stretch his legs in this race, but each time Bardet sprinted away, it was Froome who responded, with Urán marking the pair, then, almost invariably, Landa catching up as well.

The repeated accelerations saw off first Yates, and then Aru, who both “did the elastic” as the slang has it, dropping off then clawing his way back just in time for the next increase in pace to begin the whole painful process again. By the summit, Aru was 13sec behind Froome, Landa, Bardet and Urán, with Yates further back. The gaps widened on the 28km descent, and by the finish Aru had lost 31sec, pushing him down the standings to fourth.

Roglic, however, had already taken flight for a victory which Contador had done his utmost to claim. The Spaniard has not won a Tour stage since 2009, but played a tactical blinder here, placing two team-mates, Bauke Mollema and Jarlinson Pantano, in the early escape of 33 riders, bridging to the move on the Col de la Croix de Fer, then using his colleagues to forge what should have been a stage-winning gap by the foot of the Galibier.

Contador was unlucky to fall upon Roglic, a former junior ski jump champion who has been climbing well in this Tour, but is better known for winning a time-trial stage in the Giro d’Italia in 2016. When Roglic made his final move 6km from the top of the Galibier – after a certain amount of sparring with Contador and the Tour de Yorkshire winner Serge Pauwels – the Spaniard had no answer.

Facebook Twitter Pinterest Stage winner Primoz Roglic descends the Col du Galibier. Photograph: Bryn Lennon/Getty Images

As the leaders passed the Henri Desgrange monument atop the roof of the Tour, the mountains leader Warren Barguil sprinted past Contador as if he were standing. As an image of the new generation ousting the old, it could hardly have been bettered. Now in his 35th year, Contador will not retire until the end of next year; this was supposed to be his last Tour but now he is sounding less certain.

There were time bonuses up for grabs for second and third place behind Roglic; Urán has been best at this game and snatched 6sec, while Froome took four. The upshot is that Urán and Bardet are equal on time in second and third, 27sec adrift, which is the kind of margin that can be lost, won or entirely obliterated in a few hundred metres on the Izoard. Yates, meanwhile, lost 1min 30sec to his direct rival for the under-25 prize, Louis Meintjes, but still has 2min 28sec in hand.

If yellow and white are still in abeyance, the green and polka-dot tunics are all but decided. The points battle was cut short when the five-times stage winner Marcel Kittel abandoned after an early mass pile-up in which the British champion Steve Cummings ended up head over heels in the middle of a field. That places Michael Matthews in green by 160 points – uncatchable in other words – his team‑mate Barguil, meanwhile, has a solid margin at the head of the mountains standings in spite of wounds sustained in the same crash.

Kittel’s departure ended a bitter couple of days for the Quickstep team, now down to six, while the FDJ squad is reduced to three after Thibaut Pinot’s departure. And the Alps also ended the daily torture suffered by the British sprinter Dan McLay, who had survived many battles with the broom wagon and the time cut, but abandoned at the foot of the Galibier when it was clear this was not one he could win.

Stage 17 results (La Mure to Serre-Chevalier, 183km): 1) Primoz Roglic (LottoNL-Jumbo) 5h 7m 41s. 2) Rigoberto Uran (Cannondale-Drapac) +1:13”. 3) Chris Froome (Team Sky) ST. 4) Romain Bardet (AG2R La Mondiale) ST. 5) Warren Barguil (Team Sunweb). 6) Mikel Landa (Team Sky) +1:16”. 7) Daniel Martin (Quick-Step Floors) +1:43”. 8) Alberto Contador (Trek-Segafredo) +1:44”. 9) Louis Meintjes (UAE Team Emirates) ST. 10) Fabio Aru (Astana Pro Team) ST.

How it feels to tackle the Tour de France's 'final battle' – the Col d'Izoard Read more

General classification after stage 17: 1) Chris Froome (Team Sky) 73h 27m 26s. 2) Rigoberto Uran (Cannondale-Drapac) +27”. 3) Romain Bardet (AG2R La Mondiale) ST. 4) Fabio Aru (Astana Pro Team) +53”. 5) Mikel Landa (Team Sky) +1:24”. 6) Daniel Martin (Quick-Step Floors) +2:37”. 7) Simon Yates (Orica-Scott) +4:07”. 8) Louis Meintjes (UAE Team Emirates) +6:35”. 9) Alberto Contador (Trek-Segafredo) +7:45”. 10) Warren Barguil (Team Sunweb) +8:52”.

New route for La Course

The fourth edition of La Course will break new ground on Thursday as the women’s race expands into a two-stage event for the first time. La Course had been run for the past three years as a criterium on the Champs Élysées circuit on the final day of the Tour de France, a format which drew criticism from top racers such as Lizzie Deignan and allowed sprinters to dominate. The women’s peloton will first fight it out on the formidable Col d’Izoard climb on a 67.5km stage on Thursday before a pursuit in Marseille on Saturday. Deignan will be flying the flag for Britain but Annemiek van Vleuten – who crashed horrifically at the Rio Olympics – is one of the favourites for the first stage.