McLaren's Pedro de la Rosa topped the timesheets on the first day of testing at Jerez.

In bright sunshine, with temperatures reaching almost 20 degrees, nine teams got to work in preparation for the new season, which gets underway in a little over four weeks.

The Spaniard was joined by Valencia pace-setter Lewis Hamilton as both drivers concentrated on long runs in the morning, completing a full race distance over three separate stints. The focus for the afternoon was further set-up evaluation alongside work on the on-going aerodynamic and engine development programmes.

Williams got its 2007 preparations off to a perfect start with Alexander Wurz finishing second quickest in the new FW29, which was only launched last Friday. The Austrian completed 73 laps finishing a mere 0.020s down on the leading McLaren. However, an unspecified technical fault caused the former McLaren test driver to stop out on track with minutes of the session remaining.

Nico Rosberg was also on duty for the Grove outfit, in the second FW29. The German completed 64 laps, finishing 0.525s off the pace.

"Today was the FW29’s first run and we had two cars on track straight away," said Technical Director, Sam Michael. "Completing 611kms in total on the first running day with no issues with temperatures, vibrations etc., is a good start.

"Motivation within the team is really high," he continued, "and everyone is pushing hard to get the best out of the car before the first Grand Prix. Both drivers started testing different set-up packages before midday as there are some interesting new directions with this car and the Bridgestone Potenza tyres. We'll continue with that work tomorrow."

BMW was represented by Robert Kubica and Sebastian Vettel. The German started the day doing a baseline set-up, in addition to practice starts and an aerodynamic comparison. The Pole also did some aero evaluations. He then began working on the set-up and was able to make considerable progress. However, both drivers subsequently lost time due to hydraulic problems.

Kimi Raikkonen and Luca Badoer were in action for Ferrari, the Italian outfit having two F2007s available for the first time. Originally, Felipe Massa was scheduled to partner the Finn, but the Brazilian was forced to withdraw at the last minute having gone down with a "fever".

Ralf Schumacher and Franck Montagny put the TF107 through its paces as the Japanese team tried out several set-up options ain an attempt to gain data. However, progress was checked in the afternoon as Montagny's day ended an hour early when his car stopped at turn six while Schumacher's afternoon was disrupted by suspension changes which also cost time.

"It is still only the second week of testing with the new car," said Test Team Manager, Gerd Pfeiffer, "so we were continuing to check various systems as well as also working on set-up.

"We gained a lot of useful information from both cars today but, as expected in testing, there were one or two issues which cost us time. Franck unfortunately caused a red flag when he suffered a transmission problem and had to stop on the track. Ralf had to wait during the afternoon for a minor oil spillage around the engine to be cleaned and we also made some suspension set-up changes which took time.

"Despite this, we did some valuable work to build on what we learned at Valencia last week," he concluded.

Jenson Button spent his early laps finding a good balance on the RA107, which is running at Jerez circuit for the first time. The Englishman then concentrated on tyre and aero evaluations, completing a total of 99 laps.

In the RA106, Christian Klien had a quieter day as the testing schedule for the car reaches its conclusion. The Austrian completed some electronics controls work and race start simulations.

Button will continue his programme tomorrow, with Indy Car driver Marco Andretti joining the team for the first of his two days of running in the RA106.

Although the top ten cars were covered by just 0.692s, indicating just how tight things are at this stage - at least under pre-season test conditions - the Red Bulls were off the pace, as were the Renaults and Christian Klien (Honda).

David Coulthard, in the RB3, finished eleventh quickest, having completed 48 laps, with Mark Webber, in the second RB3, fifteenth, having completed just 27 laps.