The start of the days testing was delayed due to foggy weather in the morning, grounding the medical helicopter until conditions improved later in the morning.

Both drivers would work on the new FW26 and by the end of the day Marc would be second and Ralf fourth in the times. The team had a new third FW26 available for the drivers. Ralf was returning after having been forced to finish early his testing at Valencia due to stomach pains.

Both WilliamsF1 drivers spent the day working on the setup of the new FW26, including mechanical and aerodynamic. Ralf would complete sixty four laps, with a best time of 1m:16.016. Marc completed fifty nine laps with a best time of  1m:15.302.

Both drivers were headed by the BAR's of Jenson Button and Takuma Sato in first and third respectively. Button had set a new circuit, while running light on fuel, to be almost 1.5 seconds ahead of Marc.

WilliamsF1 Test Team Manager Tim Newton commented on the days testing: “Despite the delay this morning due to the heavy fog, we’ve had a productive session during our first day at Barcelona. Ralf shook down the new, third chassis of the FW26 and then finished the day setting up the car. Marc similarly completed set up work on the second FW26 as well as practising starts and performing some longer runs.“

Tomorrow Nelson Piquet will join Ralf and Marc.

Pos Driver Team-Engine Tyres Time Laps

1. Button BAR-Honda (M) 1:13.867 27
2. Gene WilliamsF1 BMW (M) 1:15.302 59
3. Sato BAR-Honda (M) 1:15.594 75
4. R. Schumacher WilliamsF1 BMW (M) 1:16.016 64
5. Badoer Ferrari (B) 1:16.302 81
6. Fisichella Sauber-Petronas (B) 1:16.584 85
7. de la Rosa McLaren-Mercedes (M) 1:16.955 59
8. Wurz McLaren-Mercedes (M) 1:17.069 35
9. Turner McLaren-Mercedes (M) 1:19.887 17