Going into the Alps, Aru was second overall, breathing down Froome’s neck.
“Certainly at this point it’s my race to lose”, Froome said.
“We took the roundabout the wrong way and he (Boasson Hagen) took the shortest way”, admitted Keukeleire.
“Everybody else following me did the same”.
A day after the final mountain test, the organisers threw the longest stage of the entire Tour at the riders as they rode 222.5km from Embrun.
The trundling Sky-led peloton arrived 12 and a half minutes after their former team-mate.
It will take something of a miracle to stop Froome, the strongest time trialler of the trio, from winning his fourth Tour de France.
“It was cool seeing Didi out there, he’s a legend of the Tour”, Froome said. “I understood that going right would be quicker”. The start and finish are both at the Stade Velodrome, home to the Olympique de Marseille football club.
Although Froome is favoured to gain time in a battle against the clock, he has little margin for error.
Arndt placed second, five seconds back. Bardet and Uran are the only riders within a minute of Froome, after Italian Fabio Aru again faded on that climb and continued his slide down the overall rankings.
“I had studied the course and I knew I had to go right in that last roundabout. I won’t take any big risks like in Duesseldorf, but when I can push, I will push”.
The 26-year-old Matthews, victor of stage 14 in Rodez and the 16th stage in Romans-sur-Isere, had built up a huge 160-point lead over Germany’s Andre Greipel by Friday’s stage. And one of those is a time trial race against the clock, a discipline he excels in – having provided him with bronze medals at the Olympics of 2012 and 2016.
Much was made of the aerodynamic skinsuit Sky wore – with the UCI race jury dismissing claims from rival teams that it was illegal.
He is now guaranteed to win the polka-dot jersey awarded for points collected during the Tour on climbs – an even more impressive feat considering he suffered a pelvis fracture in a crash in April and was struck by a auto on a training ride past year, fracturing his wrist.
Yet Boasson Hagen was a deserving victor, with the Norwegian coming off second-best in two photo finishes in this year’s Tour.
The Team Dimension Data rider was denied by just six millimetres – or 0.0003 seconds – when Marcel Kittel won stage seven to Nuits-Saint-Georges in the first week of the Tour.
Add in two third places along the way, and he was due a victory.
“I’m so happy, it worked out really well. I didn’t have to have a photo finish so I’m very happy about that”.
Inside the final 20km, an attack from Belgian Keukeleire, who was voted the most combative rider of the day, split the lead group with a front nine forming.
At the finish of Stage 19 in Salon-de Provence, Boasson Hagen and German rider Nikias Arndt went right around a roundabout while others went left. Nikias Ardnt and eventual victor Edvald Boasson Hagen went right and opened up a 20m gap that couldn’t be closed.
“Nikias made an attack and I followed him”.
There was better news for Arndt’s Sunweb team-mate Matthews, who is now mathematically assured of keeping the green jersey as leader of the points classification as long as he makes it to Paris. “I finally got my victory”.
“Maybe that has affected my performance in the last couple of days, but all of my dreams have really come true”.