Mark Webber emerged on top of the pile as the final F1 test of the winter kicked off in mixed weather conditions at the Circuit de Catalunya in Spain.
As was the case on the final day of the previous test at the circuit near Barcelona, poor weather would be a factor in proceedings, with rain showers throughout the morning leaving playing havoc with team's testing programmes.
As the afternoon session wore on however, so the circuit started to dry out, giving drivers the opportunity to switch to intermediate and then to dry tyres in the final hour.
In the end it was Webber who emerged on the top of the pile during a frantic final spell, posting a best time of 1min 22.693secs at the wheel of Red Bull's RB9. Although not as quick as team's managed during the previous four-day test, it was more than enough to give the Australian top spot on day one with Mercedes' Lewis Hamilton well over a second behind.
Hamilton was the busiest man on track as he completed a total of 113 laps, nearly double the tally completed by Jean-Eric Vergne after he went third quickest for Toro Rosso. The Frenchman had earlier been the pacesetter first thing in the morning when running on a wet circuit.
“Not the best of days, because we had many things to test and the rain meant we were not able to get that much done, but we have to remember that the other teams have similar programmes and the rain affects everyone,” he said. “Nevertheless, I did plenty of laps, which is good for me and good for the new car to do a high mileage. The car seems to behave really well in the wet and it also felt good in the dry, during the few laps I managed at the end of the day.”
With conditions on track resulting in large gaps between the drivers, Valtteri Bottas was fourth for Williams, with the top six completed by Sergio Perez's McLaren and the Sauber of countryman Esteban Gutierrez.
Paul di Resta, no longer the sole confirmed driver at Force India after the signing of Adrian Sutil, was seventh quickest ahead of Felipe Massa's Ferrari, with the Brazilian causing a late red flag when he stopped on the circuit.
It would be one of a number of stoppages during the day, with Gutierrez and Romain Grosjean both causing red flags when they went off in the wet during the morning.