Toro Rosso's Sebastian Vettel topped the timesheets at the end of the first day of testing at Jerez today, the first of four days action at the Spanish track, and the final test before the Summer ban.

Nine teams were on duty, but Vettel and Jarno Trulli were the only GP regulars in action, on a day when conditions were ideal throughout.

With track temperatures reaching 51 degrees C in the afternoon, Vettel set his best time in the cooler morning session, on his way to completing his programme. Aero testing followed by mechanical work aimed at improving set-up and traction were the first items on the agenda. Brake materials were also evaluated and the day ended with more aero testing. Vettel continues driving tomorrow, when he will run the entire day on 2009 specification slick tyres.

Gary Paffett was second quickest in the McLaren, the Englishman completing 80 laps on his way to posting a best time just 0.335s shy of Vettel's.

Luca Badoer took to the track for Ferrari as the Maranello outfit worked on two main areas. The morning was dedicated to comparing various different aerodynamic solutions, while in the afternoon, he ran slick tyres in preparation for the 2009 season, with the consequent modifications to the aerodynamics on the F2008, to try and replicate the levels of downforce that will be required starting next year.

"We completed our planned programme," said Badoer. "This morning it was important to go deeply into some technical elements to understand what happened last Sunday in Hockenheim. We picked up a lot of data, and that will continue over the next few days when we also test some solutions for the forthcoming races."

Nico Hulkenberg was on duty for Williams and though he posted the fourth quickest tome of the day, the German was only able to complete 58 laps.

"Nico concentrated on general set-ups," said Test Team Manager Dickie Stanford. "However, our running was cut short by a technical problem later on in the afternoon, though fortunately didn't lose too much time."

Sebastian Buemi had a good day for Red Bull, the Swiss driver working mainly on suspension, as well as carrying out other development work, both short and long term. Mark Webber takes over tomorrow, when part of the Australian's programme will involve running slick tyres.

Romain Grosjean, who won the GP2 Feature Race at Hockenheim only to be subsequently demoted to second, was in action for Renault. Having tested for the team for the first time last month in Barcelona, the young Frenchman was delighted to have another chance to work with R28.

The French team focussed on getting Grosjean comfortable with the car and completed some R&D work in the afternoon. He covered 71 laps finishing sixth on the timesheets.. Nelson Piquet will drive for the next couple of days as the team continues with its development programme. However, Grosjean will remain in Jerez to observe the team before returning to the cockpit for the final day on Friday.

"It was my first time here in Jerez," said the Frenchman, "and so I had to learn the track this morning and worked gradually with the team improving the car throughout the day. It still feels amazing to drive this car and I was glad to have the chance to work with the team again. It was quite difficult today because of the high temperatures, but I really enjoyed driving this circuit with the mix of high and low speed corners. I'm now looking forward to observing the team for the next couple of days to learn as much as I can."