Britain’s Geraint Thomas moved a step closer to winning his maiden Tour de France after pushing Sky teammate Chris Froome down the standings on a 17th stage won by Colombia’s Nairo Quintana on Wednesday.
Thomas held an overnight lead of 1min 39sec on compatriot Froome, but took it to 2:31 after the four-time champion crossed the finish 1:36 behind Quintana and nearly a minute off Thomas.
Ireland’s Dan Martin (UAE) finished second at 28secs behind Quintana, with Thomas third at 47 and Slovenian Primoz Roglic (Lotto-Jumbo) in fourth at 52.
Froome’s failure to stay with Thomas in the final few kilometres of the 16 km climb to the finish of the Col du Portet amid a series of attacks by rivals means the Kenyan-born Briton is in danger of finishing off the podium.
Dutch rival Tom Dumoulin, the 2017 Giro d’Italia champion, finished behind Thomas but well ahead of Froome to move up to second place.
Roglic, meanwhile, moved up to fourth overall just 16secs behind Froome.
Welshman Thomas will start Thursday’s 18th stage, a mainly flat 171 km ride from Trie-sur-Blaise to Pau with a 1:59 lead on Sunweb team leader Dumoulin, with Froome in third.
“It was just about defending that lead,” said Thomas. “But it’s the Tour de France, so anything can happen.”
Froome appeared to abdicate his crown when he tipped his hat to Thomas at the finish.
“Geraint deserves to be in the yellow jersey, he’s earned it,” said Froome.
Friday’s stage is the final day in the mountains, but has a downhill finish in Laruns, meaning any advantage rivals may manage to snatch from Thomas on the ascent could, theoretically, be annulled by Sky on the descent.
Quintana said: “I’m happy for the win. It was a day for the pure climbers.
“It’s also great for the morale of the team. It’s been frustrating, and sad because things didn’t work out the way we’d hoped.
“But we have to keep on fighting.”
Tour organisers introduced innovation with the top 20 placed riders, much like in Moto GP, starting on a grid according to their times in the general classification.
At only 65 km long — a nod to the number of the French department featuring the start and finish (65) — and with three punishing climbs, a spectacular day of racing looked to be on the menu.
But when it came to rival teams trying to loosen Sky’s grip, it was the same old story.
An early breakaway sparked by Estonian Tanel Kangert (Astana) and ‘King of the Mountains’ Julian Alaphilippe eventually came to nothing, although the Quick-Step rider picked up 18 precious points for his polka dot jersey.
Quintana overcame two mechanical problems early in the race, when he twice had to chase back to join the peloton.
When Martin attacked at the foot of the final climb, Quintana was quickly on his wheel.
Safe in the knowledge Quintana was unlikley to claw back his overnight deficit of nearly four minutes, Sky let the Colombian go.
They only had to control Dumoulin and Lotto Jumbo rider Roglic, who launched a series of attacks in the closing kilometres that put Froome in trouble.
Quintana, having benefited from the help of teammate Alejandro Valverde after he got into an earlier counter-attack, attacked solo with 6.4 km remaining.
Martin battled to close the gap, but came up short as the Colombian claimed just his second Tour stage five years after winning at Semnoz in the Alps.
The final podium placings will be decided by the penultimate-stage time trial, over 31 km, on Saturday.