BBC Sport's Lee McKenzie and Ben Edwards assess the first Formula 1 test of the season as the cars go on track for the first time.

Jenson Button topped the timesheet at Jerez in his McLaren on day two, while Nico Rosberg finishing just short of completing 100 laps for Mercedes, while world champion Sebastian Vettel has had a torrid start to his pre-season testing, completing just 11 laps over the first two days in his new Red Bull.

Vettel's 11 laps compares unfavourably with the 174 he had done at the same stage last year.