Sebastian Vettel's British GP tyre failure cause may remain unknown

Vettel hit trouble two laps from home at Silverstone last weekend when his front left tyre deflated on the run down to Brooklands

After going off at Luffield, he was able to pit for fresh rubber but dropped down the order from fourth to seventh.

With Kimi Raikkonen having suffered a tread failure on the previous lap, Pirelli launched an immediate joint investigation with Ferrari to try to unlock exactly what happened.

Work on Vettel's tyre has concluded that the failure was triggered by a slow puncture, and it was running it with nearly zero pressure inside that led to the structure breaking close to the shoulder.

But what Pirelli cannot determine for sure is what caused the slow puncture itself - primarily because the tyre had got so damaged by the time Vettel was able to bring it back to the pits.

Forensic examination of the parts, including the internal belts, has shown no suggestion of anything abnormal that would have triggered the problems.

It could be that the puncture was caused by debris somewhere on track, which Vettel's tyres would have been more susceptible to because they were 32 laps old. But Pirelli says this can never be proven.

Work is still continuing on Raikkonen's tyres to try to work out what happened on his car.

A statement from Pirelli said: "Kimi Raikkonen's damaged tyre shows less evidence of what occurred, so further tests and analysis are still ongoing in Pirelli's laboratories and indoor testing facilities.

"It will take a few more days to reach a definitive conclusion."