Ahead of today's opening practice session, the air temperature is 16 degrees C, while the track temperature is 23 degrees C. It is bright and sunny.

Although it is only two weeks since the last Grand Prix, much work has been done during that times, with several teams looking for a significant step forward this weekend. McLaren and Ferrari, in particular, will be hoping for a major turn around in performance. Following its dreadful performance in Bahrain, BMW also, will be looking to rediscover the sort of form shown in 2008.

When the lights go green, Timo Glock leads the way, followed by Bourdais, Vettel, Sutil, Heidfeld, Buemi, Alonso and a whole host of others.

While most drivers return to the pits, having completed the obligatory installation lap, Bourdais and Webber both continue round to complete a second lap.

Massa is the first of the Ferrari drivers to go out, the Brazilian running with a 'traditional' diffuser. The Maranello outfit has built a new lighter chassis for Kimi Raikkonen which is fitted with a new diffuser but not the 'double-decker' type being used by some of his rivals.

However, it is the BMW F1.09 which features the most changes this weekend, with a whole raft of new components including a new nose, new front wing, new rear wing and lots, lots more.

The tyre options this weekend are hard and soft.

Nine minutes into the session, everyone has been out. The waiting begins…

Twenty-six minutes into the session, Bourdais heads down the pitlane once again. Moments later, he is joined by Glock.

The Frenchman crosses the line at 1:29.551 to post the first time of the weekend. As Glock posts 24.601, Jarno Trulli heads down the pitlane.

Trulli posts 24.475 to go quickest as Rosberg gets to work, however, moments later Glock takes the top spot with a 23.924.

Trulli improves with a 23.711 as Rosberg goes fourth (25.563). Heidfeld, Nakajima and Buemi are also on track.

Having posted a time 4.414s off the pace on his first flying lap, Heidfeld heads back to the pits. The front end of the F1.09 is radically different to what e saw in the opening races, the nose is very, very flat.

Rosberg improves to second, 0.038s off Trulli's pace, as Kovalainen posts 25.208 to go eighth. Hamilton goes tenth with a 28.161, the two McLarens split by Heidfeld's BMW.

A 23.122 sees Rosberg go quickest, ahead of Trulli, Glock and Nakajima, as Massa takes fifth place with a 24.013. Kovalainen improves to ninth, Hamilton eleventh and Kimi Raikkonen goes fourteenth (25.687).

Rosberg spins at the exit to Turn 13, however, the German is able to continue. Meanwhile, Massa goes second with a 23.376, improving with a 22.855 next time around.

At 'half-time', it's: Massa, Nakajima, Rosberg, Webber, Trulli, Glock, Buemi, Vettel, Sutil and Bourdais.

The on-board camera shows that the cockpit surround on Nakajima's car has worked loose.

Raikkonen improves to eleventh but remains over a second off his teammate's pace.

Button and Barrichello are both on track, the Englishman going fourth with a 23.312 on his fourth flying lap. Teammate Barrichello takes second with a 23.035, however, he is almost instantly demoted by Trulli who posts 22.975.

Vettel goes wide at Turn 4 and takes a long drive through the gravel, on to the grass and back on to the track.

Button goes quickest with a 22.626 as Kovalainen performs a practice start. Elsewhere, Glock goes wide at Turn 4 and takes a trip through the gravel.

Kovalainen posts 24.597 and remains nineteenth, with Heidfeld, who has only completed 4 laps, in twentieth, 5.3s off the pace. Robert Kubica is currently fourteenth (23.784), 1.158s off the pace.

Rosberg posts 22.680 to go second, his team having confirmed two new sponsorship deals here this weekend, one with Hell, an energy drink and the other with Green Flag, the (car) rescue and recovery company.