As Lewis Hamilton prepared for his second outing in the car on Friday, his German team-mate proved the teething problems that beset the car in the first two days of testing are over. At least for now. Rosberg drove 148 laps of the 2.75-mile circuit. That is more than two grands prix. And he also came second on the timing tables, behind Ferrari's Felipe Massa. It was a relief for Rosberg and Hamilton – but most of all for a team who have invested so much in turning around their indifferent form of recent seasons.
This season could scarcely have got off to a worse start following their launch here on Monday. First, the car went up in flames when Rosberg gave it its first outing on Tuesday. On Wednesday, Hamilton crashed at the end of a 200mph straight because of a failure of the rear brake hydraulics. The two drivers had driven fewer than 30 laps between them.
But on Thursday a delighted looking Rosberg said: "Today was reliable for sure. I think the last few days we were unlucky because they were small things but we were unable to solve them in a day.
"We really made up for it and put a smile on everyone's face. It was a fantastic achievement to drive from Silverstone to Spa distance-wise with an F1 car with no problem whatsoever. We were very consistent and I am feeling good because I can push it straight away. I am feeling very comfortable. There is a lot of work to be done because we have a little bit of understeer, but we can cure that."
When asked if he felt exhausted, he replied: "No, I'm not. I am very happy. I am very well prepared for the new season. In previous years I was always a bit tired. I had a few pains here and there, but really I was in top form."
Sebastian Vettel, who went out for the first time on Thursday, thinks that Hamilton can win the world championship this year, but the German, who also had a long session, driving 102 laps to post the third-fastest time, says that little can be learned from the first of the season's three testing sessions. He said: "In terms of speed it's impossible to give a judgment right now because people are playing with their fuel loads. And at Jerez the tyres play a massive role.
"The circuit is very aggressive. There are too many variables at the start of the year. It's a long, long way to go. Regulations haven't really changed and it will be getting closer at the top, everyone is in the hunt, even down to Williams, who set some highlights last season.
"It was important to do a lot of laps today, to get back in the rhythm and get rid of the rust. The car feels fine."
Five minutes before the end of the session Jenson Button's car came to a halt between Turns 7 and 8. He stopped for safety reasons, with a wobbly rear wheel dissuading him from going any further.
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