Mercedes' engineers are still struggling to understand how Lewis Hamilton was able to set the fastest lap of the British Grand Prix on a set of tyres that should have been well past their best.
A new rule this year awards a bonus point to the driver who sets the fastest lap of the race and it has seen teams adapt their strategy and approach to the end of races in pursuit of the point.
The easiest way to secure the point is to fit fresh tyres towards the end of the race to have a mixture of fast rubber and low fuel in the closing stages. Hamilton's teammate Valtteri Bottas did exactly that at Silverstone, making a pit stop with seven laps remaining and setting a 1:27.406 on soft tyres.
However, Hamilton was able to beat that time on the final lap of the race when he set a 1:27.369 on a set of 32-lap old hard tyres that Mercedes were worried might not make the end of the race.
"We truthfully have no idea at all how Lewis did the fastest lap of the race on 32-lap old, hard tyres," head strategist James Vowles told the Mercedes YouTube channel. "Hardest tyre available, completely used up and yet he does a fantastic lap at the end. Well done to him, [but we have] no idea.
"Because we weren't expecting him to do that fastest lap of the race on 32-lap old hard tyres, we did actually plan for him to do an extra pit stop towards the end. It was a free pit stop. Valtteri behind had to stop anyway, he'd only run mediums at that point, so had to complete the requirement for the race of using another compound.
"And with Lewis, we very much called him in with the intention of that, giving him a fresh set of tyres and going for fastest lap. He was very comfortable with how his tyres were behaving however which is why ultimately, we left him out and as you saw, he did the fastest lap irrespective."
Speaking after the race, team principal Toto Wolff said Hamilton's lap made Mercedes' tyre data "look a little bit silly".
"The fastest lap on a 32-lap old hard tyre is very surprising. We tend to have a laugh because the engineers have that new presentation on a Sunday morning that says you don't need to go for fastest lap, it doesn't make any sense. And then he pulls one out like this, which makes the data look a little bit silly, but it's just his ability."