This decision was made after successful results of testing different prototype new constructions in Portugal.

Because 10 teams did not used all the same prototypes in Portugal, Pirelli decided to add extra tyres testing - during FP2 session, in order to allow every team to try the choice and gather set-up data for season-2021.

As in Portugal, the rules allow to use first 30 minutes of practice session for testing the tyres.

As for new construction, it is intended to improve durability in the wake of the issues which teams faced at Silverstone earlier this season.

The biggest change is to the fronts, which have a revised profile. The rear profile could not be adjusted, mainly due to the problem of testing them in Portugal with the current floors, and the risk of contact with the bodywork.

Also the testing of 2021 tyres enabled Pirelli to confirm to the FIA that they will choose which version will be settled, by the November 1.

"We tested the new prototypes in Portimao," said Mario Isola, the boss of Pirelli F1.

"And we made an analysis of the result of the test, collecting all the feedback from drivers, and all the telemetry data. It was a good validation, in difficult conditions, with a new track and so on. But we had a good result.

"We identified a prototype that is an improvement in our opinion compared to the current specification. All the prototypes we brought to Portimao had a higher level of integrity. What we were missing was the driveability and the performance of the tyres on track.

"So we supplied different tyres to the teams and identified a combination of a new front and a new rear that are an improvement, and we sent a request to the FIA for the homologation of the new prototypes."

Regarding the plan for FP2 testing of the final choice, Isola said: "This was the first time that we supplied different prototypes to different teams, in general in the past when we supplied prototypes it was two sets of the same one across all the teams and drivers.

"That means not all the drivers and teams tested the prototype that we decided to nominate for 2021.

"So we are in discussion with the FIA and the teams to test again the selected prototype in one of the next races."

Compounds for 2021 will be the same as those used currently, and only the construction will change.

"There is a slightly different front profile," said Isola. "With the rear we decided to keep the same profile because of the floor and all the issues that we can have when we fit a different profile.

"But also on the rear we are using some elements that are different, and also materials that are different.

"The difference is not huge – we are going to validate a construction that is not a completely different product compared to this year, but in terms of integrity, the result we had from indoor testing was quite promising."

Although Pirelli hasn't given any figures a set of the revised tyres will be slightly heavier than in 2020, leading to a further increase in minimum car weight.