Ahead of today's session - the first of the new season - the air temperature is 17 degrees C and the track temperature is 21 degrees. It rained overnight and has been damp most of the morning. Though it is no longer raining it is extremely overcast and windy… a good opening test for the four rookies and the new Pirelli tyres.
Daniel Ricciardo replaces Jaime Alguersuari in this session while Karun Chandhok is in Trulli's Lotus and Nico Hulkenberg will drive di Resta's Force India.
Tyre options this weekend are hard and soft.
The lights go green and Chandhok heads down the pitlane to get the 2011 season underway. He is followed by Hulkenberg, Kovalainen and Perez.
It's a dreadful start for Chandhok, who was only confirmed as Lotus test driver on Tuesday. The India 'loses it' coming out of Turn 3 and clouts the wall ripping off the front wing and leaving his right rear suspension damaged. A very, very strange incident which initially appears to be more about the car than its driver. "I don't know what happened," he tells the team.
Both Hispania drivers are standing in the pitlane in their overalls. However, neither looks as though they'll be out on track anytime soon. The crew has been working through the night to get at least one car ready - thereby using up one of its (four) curfew excemptions.
Webber, Button and Hamilton are the first of the big guns to come out for their installation laps.
Seven minutes into the session, Schumacher, Massa, Alonso and Heidfeld are all on track. All but Karthikeyan, Liuzzi and Glock have been out.
Twenty minutes into the session Hamilton is the only man on track, joined, moments later, by his McLaren teammate. The 2008 champion stays out for a second lap as does his teammate.
Towards the end of the lap Hamilton eases off, diving into the pits at the very last moment. The Woking team has made a number of radical changes to the car since it last ran n Barcelona, most notably to the exhaust, front wing, diffuser and floor.
Alonso heads down the pitlane, but after another installation lap heads back to the comfort of his garage.
After twenty-nine minutes Rosberg performs a practice start at the end of the pitlane. However, he too completes just one lap.
As Vettel heads back to the pits after a single lap, Sutil, Maldonado, Ricciardo, Schumacher, Massa and Petrov head down the pitlane.
Massa posts the first time of the day/season, crossing the line at 1:31.184. Moments later, Maldonado, giving TV viewers a good shot of the movable rear wing (DRS) in action, posts 39.981.
On his next lap Massa runs wide and off over the gravel, the Brazilian appearing to have got his DRS wrong.
Webber goes second (31.576) ahead of Hamilton (31.649), Sutil, Maldonado and Ricciardo.
No sooner has Massa improved with a 29.572 than Webber posts 29.552. Button goes fifth and Buemi sixth.
A 29.033 sees Hamilton go quickest, as Webber closes to within 0.440s with a 29.473.
Great slow-mo shots of Hulkenberg locking up as the DRS kicks in. Elsewhere, Webber posts 28.217 having gone quickest in all three sectors. Button moves up to second with a 28.915 only to be leapfrogged by his teammate who posts a 28.483.
Vettel moves up to fifth with a 30.154, the German posting personal bests in all here sectors. Next time around the world champion crosses the line at 28.434 to go second.
A 27.869 sees Vettel go quickest, the German setting his best time - much like his teammate - after seven laps.
With thirty minutes remaining, it's: Vettel, Webber, Button, Hamilton, Barrichello, Massa, Perez, Buemi, Sutil and Hulkenberg.
Schumacher goes tenth with a 29.681 then improves to seventh with a 29.135, slotting in right behind his Mercedes teammate.
Still no time from Alonso, the Spaniard concentrating on aero checks and not really going for times.
Barrichello goes fifth with a 28.489 as Rosberg messes up what looked like a very quick lap with a poor final sector.
Cameras picks up a huge chunk of rubber missing from Vettel's front right tyre as he returns to the pits.