Jarlinson Pantano takes stage 15 of the Tour de France

This stage had been earmarked by Chris Froome as a possible pitfall but there was little drama here as the race leader and his team skipped around it in relatively straightforward style and victory went to the Colombian Jarlinson Pantano of the Swiss IAM team. With little of note to describe during the stage, Froome looked back for the first time to the most intriguing moment of the second week, his foray on foot up the slopes of Mont Ventoux on Thursday after his bike was broken in a crash involving a television camera motorbike.

“It was quite a chaotic moment,” the Kenyan-born Briton said. “I got back on my bike straight away, realised both seat stays were broken and the bike wasn’t going anywhere. There was no spare bike, so I figured the best thing to was to keep going forwards, but it was also to move away from the bottleneck area. I thought I needed to get up the road here and running was my only option.”

When it comes to options, Froome's rivals appear to have fewer of them with every successive day. Here, they did not seem to have the nerves or the legs to make a wholehearted attempt to put him in trouble. On the final climb of the Lacets du Grand Colombier, the Italian Fabio Aru made a move – but one that had been flagged up with the subtlety of a steamroller as the Astana team rode hard up the preceding ascent in an unsuccessful attempt to burn off Froome's team-mates.

Perhaps the young Italian was prompted by Froome's reply when asked the day before how he rated his chances. Froome's answer was a question: "How far behind is he?" Aru was more than five minutes behind on Saturday and that is unchanged. He was joined by Alejandro Valverde but their brief foray had all the impact of a gelato melting in the 30-degree heat that belted down on the Jura.

Higher up the mountain, Romain Bardet made his move, immediately before a tricky descent that should have favoured him. His only reward was a lost pair of sunglasses, which fell off his face shortly before Sky reeled him in. At the foot of the descent towards the finish, Bardet and Valverde made a brief, abortive, attack but that was all Froome had to worry about, beyond the everyday challenges: staying safe, eating regularly and – critically in this heat – drinking enough. Once again Nairo Quintana lay low; by now the conclusion has to be that he cannot attack, rather than that he is biding his time.

Sky's relentless tactics for keeping the yellow jersey have not varied in the four years since Bradley Wiggins's victory in 2012. They hire the strongest climbers they can, capable of keeping an extremely high pace, and put them close to the race leader. They ride so fast that the effort needed to get away from the lead group is so intense that it is impossible for anyone to open a gap of any note. "You attack, you gain a few seconds, what can you do?" Adam Yates, who maintained his third place overall, said. "At the moment Sky look invincible."

The only way in which this strategy can be countered is by concerted attacking from long range to wear out the domestiques, so that the leader – in this case Froome – is left exposed and has to respond to attacks on his own. Last year, this only happened in the final two stages but Movistar were unable to press home their advantage; this year, they do not look to have the legs. Froome said afterwards he was surprised Sky had not been tested more: “I thought it would be a perfect opportunity for teams to put under us pressure, especially with [Geraint Thomas] having a puncture on the second last climb: we were a man down.”

This was a brutal course, climbing the Grand Colombier and passing through the finish line before going back up the ascent from a different direction, Les Lacets, including a short, spectacular slog up a series of hairpins clinging to a narrow ridge with a void on either side.

The stage victory was fought out up and – crucially down – the two climbs by the remains of an early escape of 30 riders, with Pantano emerging along with Rafal Majka, who crested Les Lacets marginally in front but left the road on a left-hand bend on the descent, allowing the Colombian to catch him.

On the run-in from the foot of the descent to the line, they both watched each other suspiciously, allowing a chasing pair of Sébastian Reichenbach of Switzerland and France's Alexis Vuillermoz to come close, while a few seconds further behind was the day's hard-luck story; the young Frenchman Julian Alaphilippe, probably the strongest of the escapees, but unlucky to suffer a derailed chain on the penultimate descent.

Pantano was the strongest in the sprint, although Majka had done enough during the day to take over the lead in the King of the Mountains prize. The Colombian’s win comes as his team, the Swiss squad IAM – backed by an asset management company – prepare to shut up shop at the end of the season. IAM have been a friendly, attractive presence in their four years in the peloton but they have managed little more than that; this is their first Tour stage win and it comes hard on the heels of their first stage in the Giro.

IAM’s homeland beckons on Monday, with a stage into the city of Berne, where a brace of little hills, the last one at the kilometre-to-go point, could disrupt the sprinters. Whether it is Mark Cavendish’s day, or Peter Sagan’s, or whether one of the many teams in the race who have yet to win a stage can break their duck, the bigger picture is clear. Tuesday is the last rest day, followed directly by the final four days of climbing in the Alps. Froome’s third title in four years is within his reach.

Meanwhile Dan Martin drew closer to moving up the general classification, with the Irishman taking time back on rival Tejay van Garderen.

Van Garderen had started the day sixth overall, three minutes 19 seconds off the yellow jersey of Froome one minute 44 seconds ahead of Martin. However the American cracked on the final climb of the Lacets du Grand Colombier and rolled in one minute 28 seconds behind the Froome/Martin group of contenders.

As a result Martin moved to within 16 seconds of him. He remains ninth overall but any more weakeness by van Garderen, or indeed by any of the riders ahead of him, and Martin will aim to move up.

Meanwhile Sam Bennett finished in the sprinters’ group and continues towards Paris and his first Tour finish. A sprint finish is possible on Monday’s stage to Berne, although the profile is tougher than usual and may break things up somewhat.

(Guardian service)