The first day of testing at Portimao was badly affected by persistent heavy rain, with the five teams on duty getting limited running.

For pace-setter Sebastien Buemi, in a 2008 car, this was something of a special day, as it was the first time he has driven since he was officially confirmed as one of Toro Rosso's race drivers for the 2009 coming season.

Unfortunately, the weather meant the Swiss driver's car spent the entire day shod with extreme rain tyres, as the track was damp first thing in the morning from overnight rain, which then made another appearance after a couple of hours running.

The original programme should have focused on validating the 2009 engine specification, checking the car's cooling configuration and general reliability, but the weather got in the way.

Not wishing to waste any opportunities, the team switched to working on electronics, as well as giving the F1 rookie driver the chance to try some practice race starts on a wet track.

With much to be risked by running in the slippery conditions, McLaren conducted a minimal on-track programme today, using a 2008-spec rear wing as a precautionary measure to increase downforce during the runs. Despite the weather, the team carried out a number of systems checks on the MP4-24 and will continue the programme tomorrow.

Nico Hülkenberg, the first of the Williams team drivers to experience the FW31 felt confident in the car's abilities, and reflected on the difference from its predecessors. "Straight away the new car feels okay, I feel comfortable in it and for a new car, we have also had a trouble-free morning technically, which is important. Of course everyone will want to know how it compares to the 2008 car and what the impact of the rule changes are from a driver's point of view. In truth, I cannot say too much after a few laps, because the track is 100% new to me, I have never run here and also it is pretty wet, so I have no baseline for comparison - if we were at Jerez or Barcelona in the dry, I could be a little more specific. But the important thing for today is simply to make sure we run through all the checks of the basic systems on the car and confirm everything is working as it should. So far that is the case and we can be happy."

Though he only completed 33 laps in the new Renault, Nelson Piquet was happy with the car. "It feels great to be in the R29, even though the weather was not great," said the Brazilian. "Today was all about adding miles to the car, collecting data and learning as much as we could. Hopefully the rest of the week will allow us to build on the progress we have made today."

Kamui Kobayashi was at the wheel of the Toyota TF109, which was unveiled last week. After conducting a trouble-free roll-out on Sunday, the Japanese youngster continued to work on the team's KERS system, which is being used on track for the first time this week, as well as performing systems checks and gathering information. Jarno Trulli takes over tomorrow.

"Today has gone well and I am happy with the new car," said Kobayashi. "It has been an interesting experience to drive with KERS for the first time and we are understanding more about the system all the time. This is my first time driving at this track and I have to say I am very impressed; the lay-out is really exciting and quite challenging for a driver. The weather was far from ideal, especially in the afternoon, so that meant we could not spend as much time on track as we planned."