The weather conspired to shake things up on the last day of World Series by Renault group testing at Barcelona's Circuit de Catalunya, but the two sessions again underlined who could be considered the favourites for success in 2009.

James Walker's late-morning effort for P1 Motorsport was enough to send the Briton into the regular season with the best time of the day, as rain set in over Catalunya after lunch, producing slower laps as a result. The wet track provided Carlin rookie Jaime Alguersuari with a rare chance to display his talent, the reigning British F3 champion ending the final pre-season session one-thousandth ahead of USR's Miguel Molina.

Although the track was still damp at the start of the morning session, it only took a few laps of finding their feet to persuade the drivers to opt for slick tyres as the surface started to dry out. However, just as Molina was promoting himself to the head of the timesheets, ahead of Interwetten's Franck Perera, with a lap of 1min 34.458secs, day one pacesetter Charles Pic crashed his Tech 1 Racing Dallara into the barriers.

Behind Molina, positions continued to change hands until the rain made an early return, forcing teams to take advantage of the passing shower to practice their tyre changes. The precipitation wasn't enough to keep slicks away for too long and, at the end of the morning, Marcos Martinez (Pons Racing) went faster than Molina's time to take control of the timesheets.

At the same time, Alguersuari climbed to second place - only to be forced to stop his car at the side of the track. Fairuz Fauzy (Mofaz Fortec Motorsport) then eased into top spot for a few minutes, before Walker stepped up the pace again. Setting a time of 1min 32.428secs, the Briton improved his best time from the previous day, and it proved sufficient to survive the final push of the morning, as Martinez crashed to interrupt any response the rest of the field may have had.

Walker led Fauzy and Epsilon Euskadi duo Adri?n Vall?s and Chris van der Drift on the final timesheet, and the overall order remained the same through the afternoon as the rain arrived to stay.

"I really couldn't have hoped for better preparation for the new season," Walker admitted, "We're in good shape, having completed all of our homework, and we can go to the first race with a victory as our target. It feels a bit strange to be disappointed with fourth place this afternoon, but that just shows how far we've come in the last few weeks. If we keep doing what we're doing then, hopefully, we will have a lot to smile about when we come back to Barcelona in a couple of weeks."

Testing the series' new aerodynamic configuration in the wet for the first time, the drivers were still keen to venture out and, once again, it was USR rookie Greg Mansell who proved among the most tenacious, competing a lot of laps on track and taking the lead at the start of the session.

Although the outing was interrupted by a handful of spins and red flags, Molina quickly gained the upper hand over his team-mate, only to be pipped to fastest time by Alguersuari, who ended the afternoon heading a Spanish 1-2-3, with Martinez in third.

"I'm very pleased," the rookie noted, "I was very fast through the second and third sections and I'm convinced that we can do great things this season, as Carlin Motorsport has massive potential. We still have work to do, but the times in the rain are very encouraging for the season."

Molina and USR may have something to say about that, however, having again impressed in all conditions.

"Despite the changing conditions, we are ahead, which just goes to show that we are competitive," he said of the second-year team, "We've learned to lap together with USR throughout the collective testing. We're ready!"

Leading performances - Barcelona (30-31 March):

Charles Pic Tech 1 1m 32.085s* James Walker P1 1m 32.428s Marco Barba Draco 1m 32.502s* Miguel Molina USR 1m 32.515s* Marcos Martinez Pons 1m 32.619s Oliver Turvey Carlin 1m 32.619s* Adrian Valles Epsilon Euskadi 1m 32.784s Bertrand Baguette Draco 1m 32.833s* Jaime Alguersuari Carlin 1m 33.004s* Fairuz Fauzy Fortec 1m 33.053s Riki Christodoulou Comtec 1m 33.084s* Franck Perera Interwetten 1m 33.170s* Pasquale di Sabatino RC 1m 33.264s* Chris van der Drift Epsilon Euskadi 1m 33.453s Greg Mansell USR 1m 33.506s* Anton Nebylitskiy Comtec 1m 33.649s* Federico Leo Pons 1m 33.757s* Sten Pentus Fortec 1m 33.874s* Frankie Provenzano Prema 1m 33.924s* Tobias Hegewald Interwetten 1m 34.109s* Julian Leal Prema 1m 34.162s* Daniil Move Tech 1 1m 34.521s* Mihai Marinescu Interwetten 1m 35.206s

* denotes times set on day one of two