McLaren's Pedro de la Rosa posted the fastest time of the day on the first day of a three-day test at Barcelona.

Although the session began in near perfect conditions, it was disrupted by a heavy rain shower in the early afternoon.

This being the last European test of the season, not to mention Melbourne being only four weeks away, this is a critical test, and therefore many of the test teams are supplemented by members from their race squad.

In addition to de la Rosa, McLaren had World Champion Fernando Alonso on duty as the Woking team focused on continued aerodynamics and set-up development.

Just twenty-four-thousandths of a second slower than de la Rosa was BMW's Robert Kubica, who was amongst the pace setters for much of the day. That said, the Pole was the cause of two of today's nine red flags!

Kubica mainly focussed on aero work, concentrating on the front wings in addition to testing different brakes. It was shortly before the end of the day when he stopped out on track, bringing his session to a close.

The German team wanted to give Timo Glock as many laps as possible, as this was his first proper day in the new car in favourable conditions, his previous runs having taken place in bad weather. The German did an aero test as well as systems, diagnostics and recovery work.

Fourth quickest, and continuing the good pace his team has shown since the launch of its new car, was Williams Alexander Wurz, who finished h teammate Nico Rosberg finishing ninth, less than a second behind.

"Both drivers had another encouraging day," said Mike Condliffe, "working through a series of set-up changes to confirm the characteristics of the new car.

"They both familiarised themselves with the new chicane and had the opportunity to run in both the dry and the wet."

As previously reported, both Ferrari drivers, Kimi Raikkonen and Felipe Massa, had a troubled morning, both suffering electrical problems that means they had barely completed any laps before the rain fell. Indeed, Massa's electrical problem resulted in a fire on the Brazilian's installation lap.

However, in the afternoon the Maranello duo was soon on the pace, even if they only completed just over 50 laps between them.

The Italian team's technical programme was planned to include endurance testing, set-up work and development of new aerodynamic components, however, due to the 'interruptions' this will continue tomorrow.

Jarno Trulli and Franck Montagny were on duty for Toyota, the first time Italian finishing a promising seventh, 0.6s off the pace.

"This was the first time that we have run at the circuit in its modified version," said Dieter Gass. "The new section doesn't really affect the nature of the track too much but the main target was to improve safety and that should be achieved. The weather played a big part today but the rain was forecast and we amended our schedule accordingly.

"We've got through a lot of laps today, which is good because one of our main targets for this period is to achieve good reliability for the first race. We have also done some set-up work and found out more about the new car because Barcelona is a representative track to do that. The tyres seem to behave very consistently and even though there is a tendency for rear drop-off you can see the lap times keep improving through the runs."

Renault had its 2007 line-up on duty, Giancarlo Fisichella and Heikki Kovalainen. Like it's rivals, the team has a very intensive programme to complete. On today's menu were pit stop and refuelling simulations to perfect the training of the team of race mechanics who were on hand specially for this reason; in addition, various qualifying procedures were validated for the drivers who are on duty all week.

For the French team the day went off without incident and its programme was not hampered by the rain. Tomorrow, the team will pursue its development programme on the basis of the data gathered today.

"It was a good first day's testing," said Fisichella. "The track's changed due to the new layout but the car handled well right from the start. We've got another big day's work ahead of us tomorrow."

"The car handled well straight away," added Kovalainen, "and we can use that as a base line for tomorrow's work. I was happy to get back behind the wheel.

"I love driving," he added, "and I'm becoming more and more motivated as the start of the season approaches. We all want to get the maximum out of this test."

There were some glum faces in the Honda garage, not least Rubens Barrichello, who ended the day seventeenth, 2.3s off the pace. It was a little better for Christian Klien, who was just 1.59s off the pace.