Lewis Hamilton Spanish GP Mercedes strategy call was 'magic'

Polesitter Hamilton lost out to Vettel at the start and followed the Ferrari driver during the first two stints of the 66-lap grand prix.

But when contact between the McLaren of Stoffel Vandoorne and the Williams of Felipe Massa left the former stranded in the gravel on lap 33, Hamilton used the resulting virtual safety car period to make his final stop.

Mercedes waited until lap 36, calling Hamilton to the pitlane as the "VSC ending" message appeared on the screens - and as the green flags were waved, he was already approaching his pit box.

"There was a bit of thought process in the [Mercedes race] strategy group - at a certain stage we planned to do the opposite to Sebastian," Wolff said.

"And then the magic call was the one to take the pitstop at a time when it looked like the VSC would end soon.

"Because [otherwise] Sebastian could have reacted to that, pitted next lap.

"So we timed it perfectly, I really take my hat off to James [Vowles, chief strategist] and his group of strategists."

Vettel had been almost eight seconds ahead of Hamilton before the VSC was called, but, after he responded by pitting under green flag conditions a lap after his rival, he came out alongside the Mercedes.

He had to squeeze Hamilton to the outside on exit of Turn 1 to keep the lead and couldn't break away afterwards, eventually surrendering first place with 22 laps left.

Wolff added: "You lose so much when you do a regular pitstop during the race.

"Your pitstop loss is around 21s and all cars are at speed - you lose time being stationary and by being slow in the pitlane.

"And on the VSC everyone on the track is moving much slower so the effective pitstop loss is less.

"I don't know the overall number but the actual loss is probably around 12, 13 seconds - so it is much better."

Wolff admitted that Mercedes was "on the back foot" at the end of the first stint, as Vettel pitted early for new softs, preventing Hamilton from being able to perform the undercut.

Hamilton wound up running a different strategy, going long on softs early on before a switch to mediums and a final stint on softs against Vettel's mediums.

Commenting on the wheel-to-wheel battle between Vettel and Hamilton, Wolff said: "First of all, that first defence was great, maybe a little bit on the aggressive side but that is racing.

"He [Vettel] pushed him [Hamilton] wide and, from then on, we knew we had an advantage of the soft tyre that was almost brand new. We knew we had a chance."