Jerez 4: Button flies in heat

But though Button was fastest, ultimately the hot conditions meant that the he left Spain confused over his tyre options heading into the French Grand Prix next weekend.

"It's very, very difficult to judge what to do," he said. "I spent all day concentrating on tyre compounds but I really can't decide on them because it was so hot. I think we will have to go through it all again when we run in France next Friday."

Williams test driver Marc Gene was second fastest overall. The Spaniard seems certain to be the main contender for Ralf Schumacher's seat should the German not recover from injuries sustained at Indianapolis in time for the French Grand Prix. Gene worked through a grand prix simulation today, having spent yesterday practicing pit stops and putting in low fuel runs - all indications that he is being prepared should his services be called upon.

"I haven't been officially told I will be driving in France," Gene said, " but if I get the call I am ready."

Kimi Raikkonen, on his second day of testing duty, was third fastest in McLaren's MP4-19B ahead of Anthony Davidson's BAR-Honda. The Englishman concentrated on aero tweaks that Button didn't have time to try. He was impressed by them. "It's a very, very positive step," Davidson said. Team-mate Takuma Sato tried them yesterday as well, but his assessment was inconclusive because of the 40 degree temperatures.

David Coulthard was fifth quickest in the other McLaren MP4-19B, which seems more and more likely to be brought into service in Magny-Cours, while Antonio Pizzonia recorded the sixth fastest time in the second Williams. The Brazilian only completed 11 laps as he ran out the life of various development parts for the FW26.

Toyota drivers Cristiano da Matta and Ryan Briscoe completed 232 laps between them, the Brazilian running through a mammoth Michelin tyre programme while the Australian worked on damping, shocks and set-up.

Jenson Button BAR-Honda M 1m17.221s 106
Marc Gene Williams-BMW M 1m17.308s 114
Kimi Raikkonen McLaren-Mercedes* M 1m17.471s 85
Anthony Davidson BAR-Honda M 1m17.645s 91
David Coulthard McLaren-Mercedes* M 1m17.901s 89
Antonio Pizzonia Williams-BMW M 1m18.856s 11
Cristiano da Matta Toyota M 1m18.890s 130
Ryan Briscoe Toyota M 1m18.906s 102

*Denotes MP4-19B