Button was still using a 2005-specification car while team-mate Anthony Davidson tried out an interim machine, which complies with new rules to restrict engine power.

Davidson was five seconds slower than Button, giving some indication as to speeds expected next season, when the 2.4-litre V8 engines replace three-litre V10 units.

Frenchman Franck Montagny was second quickest for world champions Renault while Jarno Trulli was third for Toyota, who are now using Bridgestone tyres following their winter switch from Michelin.

Today marked the final session of BMW-Sauber’s debut three-day test, with Nick Heidfeld once again given driving duties.

Team boss Mario Theissen was pleased with the new team’s progress after finally seeing the culmination of his work in persuading BMW to buy Sauber.

He said: “This was a successful first joint test. It was important that we could run the BMW engine in the Sauber chassis at this early stage, in order to integrate all technical systems.

“This is the beginning of the testing season, and there is naturally a lot of work to be done.

“The co-operation at the track as well as the preparation of the interim chassis went very well – it was the first joint task of the new team.”