BMW's Nick Heidfeld and Honda's Jenson Button set the pace on the first day of testing at Jerez today. However, the 0.670s gap to (third quickest) Pedro de la Rosa doesn't indicate a massive improvement in pace from the RA107 but rather the fact that two drivers were using slick tyres.

The much anticipated return of slick tyres, which will (hopefully) be reintroduced in 2009, didn't see a dramatic improvement in lap times, but this could also be due to the fact that drivers are still getting to grips with 2008-style electrics and the lack of driver aids.

Button, under the watching eye of Ross Brawn (above) who was making his first public appearance with the Brackley outfit, was the first driver to run on slicks, however, his best time was soon beaten by Heidfeld once he switched from grooved tyres.

Other than slick tyres, Heidfeld, who will be driving for three days this week, was concentrating on preparations for 2008. In particular he worked on the 2008 electronics and driving with no traction control.

The German team took this opportunity to give two young F1 hopefuls a test. In the morning, it was 20-year-old Javier Villa, who had his first taste of Formula 1 power. Prior to this the Spanish driver had raced here in Formula 3 and tested in Gp2 for just one day.

In the afternoon, it was 23-year-old Marko Asmer in the same car. The Estonian driver has tested a Formula 1 car before, but this was his first ever visit to Jerez.

Both drivers, who were separated by just 0.541, with Asmer being the quicker, completed their programmes without any problems.

Button continued the evaluation of the 2008 standard electronic controls system, which was tested for the first time by the team at Barcelona last month. This was the English driver's final F1 test commitment this year, with Rubens Barrichello taking over tomorrow.

The Honda Young Driver Programme continues, with Mike Conway, Luca Filippi and Andreas Zuber all having a second opportunity to work with the Japanese team this week.

Conway had his day in the car today and continued his acclimatisation programme from the Barcelona test as he continued to work with the engineers to understand the car's set-up. In the afternoon, he focused on longer runs before finishing the day with short new tyres runs. Andi Zuber will take over the car tomorrow.

Quickest of the non-slick runners was Pedro de la Rosa in the McLaren, who was partnered by Gary Paffett. The Woking team had two chassis at the track, one set-up to focus on aerodynamic development and the other on the proving of chassis components. The Spaniard and the Englishman swapped between the chassis during the day.

Lewis Hamilton will join de la Rosa tomorrow for two days, with Paffett returning for Friday when the team will run with slick tyres.

Just under three weeks after having his World Championship title officially confirmed, Kimi Raikkonen was back in the cockpit at Ferrari, the Finn preparing for the defence of his title in 2008.

The Finn was joined by Marc Gene as the Italian outfit worked on the development of new components for 2008, with special emphasis on electronics.

Following on from the work conducted in Barcelona last month with Heikki Kovalainen, Renault, which has Nelson Piquet on duty this week, is looking to make the most of its final on-track running for over a month.