Kevin Magnussen made a spectacular debut with McLaren today, the rookie posting the quickest time as Mercedes power units continue to set the pace.

The German engines powered four of the six quickest cars, whilst the Renault powered cars were well off the pace and managing only forty-three laps between them.

Following Monday's problems, when McLaren failed to turn a wheel, the Woking outfit gave Jenson Button an extra half-day in the MP4-29. The Briton continued the evaluative work he began yesterday, further drilling down into the detail as he continues to understand and refine the car.

After lunch, Magnussen took over for his first run in the car. The team had devised a programme that gave him maximum time in the cockpit. This meant focusing on a series of longer runs - in order to best familiarise him with the car and its systems. Additionally, he conducted some shorter runs at the end of the day, punctuating them with a series of practice starts in the pitlane, and some practice pit stops.

"This was a big day for me," said the Dane. "I had butterflies in my stomach and had trouble sleeping last night - I'm a rookie, and I was just excited to get in the car. Equally, however, this doesn't feel like my first day at work: I know everybody at McLaren, so I really felt at home.

"Happily, everything worked as it should," he continued, "and the car felt good. I'm pretty pleased with our reliability - to have done as many laps as I did in just half a day was pretty positive. I'm not taking too much from the fact that I set the fastest time - I was pushing, but it wasn't a balls-to-the-wall lap. We wanted to get good data and learn about the car, so I think everyone is pushing out there.

"Even so, I still think we can improve the car this week. And the most important thing is to understand how to improve things when we go away from here. I think we have a good idea of the direction to take."

While Magnussen ended the day fastest overall, more pleasing to the Woking team was the fact that the car - in the hands of both drivers - completed a total of 92 laps, more than any other team, thus underlining the team's pre-season aim to focus on reliability over performance.

Second quickest was Felipe Massa, making his debut for Williams. The Brazilian completed 47 laps as he focussed on new component, systems and reliability checks.

"It was a new experience for me today," he said. "The first day with a new car is always very exciting but adding to that changing teams, all the new faces and the new place, it made it even more exciting for me.

"Unfortunately we didn't do the amount of laps we wanted to do today," he continued, "but it's pretty acceptable for the first days of testing considering all the rule changes with the car.

"The car feels very different to what we used to have in many areas. You need to understand how to drive with the engine, the chassis, the tyres and the turbo, but it's fun! There will be a lot of improvements we can make up before the first race and throughout the championship. Performance is important but I think reliability will be a key issue to think about for the first race.

"I'm happy with how I have been welcomed into the team as everyone has been very kind and professional. I'm really happy and I know we have a lot of work to do to fix the little issues we have, but I think we can have a good championship together. It's also my first experience with a different engine manufacturer and it's been really great working with Mercedes. I'm really happy with the new power unit and the way the team work so it's going to be interesting. Overall, I'm very happy with my first day."

"Felipe's done quite a bit of work in the simulator at the factory, so it was good to get his comments on the real thing as opposed to the digital version," said Rod Nelson, the Grove outfit's Chief Test & Support Engineer. "We got some really good feedback and have a clear direction to go in from both our drivers this week despite the slightly limited mileage. We are working through our system tests here in Jerez and are coming across a few issues which we are resolving. Overall, we are relatively happy with the progress we are making."