Jenson Button made a positive start in his first outing in the new McLaren MP4-29 on Wednesday as he was fastest after the morning session on the second day of pre-season testing in Jerez, southern Spain.
The British driver had suffered a frustrating day on Tuesday as the newly modelled car, built to comply with a series of new technical regulations, failed to make it out of the garage and onto the track.
However, on the day McLaren announced that former Lotus team principal Eric Boullier would be joining as the team's new racing director, Button made a confident start as he completed 13 laps with his best effort of 1min 36.094secs putting him over a second ahead of the competition.
Williams' Finnish driver Valtteri Botas was second fastest, while Ferrari's Kimi Raikkonen was down in third.
It was another quiet morning for reigning world champion Sebastian Vettel, though, as having completed just three laps on Tuesday, he added only a further four to his tally early on Wednesday.