Last week Button said he was "frustrated" by his first day of testing in Valencia, as he hadn't been able to get his seating position right. But after two days in Jerez, where he set the third fastest time of the week so far, he said he was finally comfortable with the MP4-25 and was making progress.
"For me, today was a better day because we could get out in the dry," Button said. "It is the first real time that I have felt good in the car, good enough within the car to actually do set-up work and find a balance with the car. And also work with different components that I prefer. So today was a positive day. There is still a lot of work to do with the car. But the basic car itself is a good baseline. But I also know that there is a long way to go before we will have a car that is capable of winning races. But that is the same for everyone. This is just testing and we have a long way to go."
Button completed 83 laps on Thursday, considerably less than some of his competitors, but said there were no problems with the car's reliability and he was happy with the work he completed.
"It is not about just going out and putting in as many laps as possible," he said. "We know that our car is reliable, and that is important. Normally that is why you do so much mileage. But when you are testing different things, you don't necessarily need big mileage. So we were doing a lot of back-to-backs and set-up work. For me that is more important than putting big distances on the tyres. So I am very happy with the way the program was today."
Lewis Hamilton will take over testing duties for McLaren on Friday and Saturday.
The 'Arena Complex' was originally designed for MotoGP, but when Silverstone won back the contract to hold the British Grand Prix from Donington, it immediately approached the FIA and Formula One Management (FOM) for approval to hold the race on the new piece of track. On Thursday FOM gave the final green light to use the new loop, which organisers are hoping will improve viewing for spectators as well as spicing up the racing.
"The 'Arena Complex' was always designed with both two and four-wheeled racing in mind," Silverstone's managing director Richard Phillips said. "We have been very careful, working closely with drivers and riders, to make sure we are improving and enhancing what Silverstone already has to offer - from a driver's, rider's and spectator's point of view."
The new F1 circuit will retain the majority of the high-speed track, but will lose the Abbey Chicane, Bridge Corner and the left-hander at Priory - all of which will remain intact to provide an alternative layout. Instead the drivers will now turn right at Abbey, before entering a 90 degree right-hander that opens into two left-hand turns linking the track to the existing National Circuit and eventually the old F1 circuit. The extra length is expected to increase F1 lap times by four seconds.
"Some will miss not seeing modern day F1 cars accelerating through Bridge, but we have to move with the times and continue looking at ways to improve the overall experience," said Phillips. "The new layout will bring an extra dimension to Silverstone, a new challenge for the drivers, and will enable fans to get closer to the action."
The £5 million 'Arena Circuit' extension is just the start of an extensive redevelopment programme that should see the pit and paddock area moved to the straight after Club Corner by the end of 2011. Silverstone has undergone a number of redesigns in the past, most notably the creation of the Complex towards the end of the lap in 1991.