Toto Wolff and his team left visibly shell-shocked after Red Bull wins French GP to extend championship lead.

"Lewis, this one is on us," Mercedes strategist, James Vowles told Lewis Hamilton in the moments after the chequered flag fell at Paul Ricard.

"Thank you for doing everything you could to recover that race," he added. "You drove incredibly well."

Benefitting from an early mistake by title rival Max Verstappen, Hamilton led the first 18 laps of a fast and frantic French Grand Prix.

Pitting a lap after his title rival, the Briton fully expected to emerge ahead of the Red Bull, but instead rejoined the race behind Verstappen and race leader Sergio Perez following what proved to be a remarkably powerful undercut.

With the main contenders all likely to have to complete 35 or more laps on hards, it soon became clear that the white-banded tyres might not go the distance, and on lap 32 Red Bull turned the race on its head by switching the championship leader to a two-stop strategy.

On the faster mediums, Verstappen began to reel in the Mercedes pair, first Valtteri Bottas and eventually Hamilton, who was unable to offer any resistance.

"Car performance was good, I think we had the quicker car probably," said Toto Wolff at race end. "We lost the race at the stop, thinking that we had enough protection against the undercut, which we didn't.

"We had a solid three-second gap to protect against the undercut and that wasn't enough, and from there on we were on the back foot actually. The fight between the three cars was intense at the front and I think you then basically had to opt to continue with the one stop or the two.

"The two stop was a danger for us because Perez was in the way, and we got it wrong today," he admitted.

Ironically, it was initially Mercedes that blinked first, pitting Bottas on lap 17, and it was due to the fear of the undercut from Hamilton also that Red Bull opted to pit Verstappen.

"We had a good opportunity to win and get both cars on the podium so the result is obviously very disappointing," admitted Mercedes engineering boss, Andrew Shovlin. "Lewis had control of the race in the first stint and if anything we looked to be a bit better on degradation.

"We triggered the stops ourselves with Valtteri who was struggling with a growing vibration and that was clearly earlier than we wanted to come in but it was getting to a level where we didn't have an option.

"Max obviously took the next lap to protect against Valtteri but with Lewis having just over three seconds of margin, we thought that he would have just enough protection from the undercut but that wasn't the case.

"The pit stops were good, the hard tyre was obviously quick but there's more that we need to go through to understand why we lost the place."

Asked about the first stop, and how he took Mercedes and Hamilton totally by surprise, Verstappen admitted: "My out-lap was good, but I didn't expect the undercut to be so big.

"When I went out, suddenly I had so much more grip on the tyres everywhere," he continued. "I don't know how fast how Lewis' stop was or whatever, I need to look at it again. But I think nobody, even us, expected to undercut Lewis.

"It clearly shows that with new tyres, the tricky conditions out there, when you are on new tyres it's easier to lose the car a little bit or whatever because of the wind.

"When you have new tyres, you have one lap where it feels a lot better. As soon as I was ahead, the next few laps, they didn't feel great anymore."

Check out our Sunday gallery from Paul Ricard, here.