Ahead of today's sole free practice session, the air temperature is 31 degrees C, while the track temperature is 40 degrees. Humidity is 63%, however, there are some ominous black clouds hanging over the far side of the circuit.

While the fall out over 'lie-gate' (sorry!) continues, the other big story is that Rubens Barrichello will drop five places on the grid tomorrow after his team opted to change the gearbox in his car. This year, the gearboxes are meant to be used for five races.

On the countdown to the green light, one minute to go, Nico Rosberg is told that there are a "few spots of rain" on the far side of the track.

The lights go green and a whole heap of cars take to the track, fully aware, like Rosberg, of the threat hanging overhead. Within three minutes, everyone has been out for an installation lap.

After the initial burst of activity, all goes quiet as the drivers wait in their garages, the minutes pass by.

Ten minutes into the session, Timo Glock heads down the pitlane. Following a practice start, he takes to the track. Moments later, he is joined by his Toyota teammate.

As Glock begins his first flying lap of the day, Raikkonen, Massa, Heidfeld, Button and Hamilton leave their garages.

The German crosses the line at 1:40.396, with Trulli posting 40.130 moments later. Sutil goes quickest with a 39.365, as Massa takes second with a 39.887.

Button and Piquet post good times, but Sutil remains quickest until Barrichello crosses the line at 39.226 to take the top spot.

A 39.174 sees Massa go quickest but this is soon beaten by Button (38.601), with Barrichello and Kubica both on hot laps. The Brazilian makes it a Brawn 1-2 with a 38.668 as the Pole takes third with a 38.868.

Webber goes quickest with a 38.226, as Raikkonen improves to fourth with a 38.850. The order is constantly changing, with Alonso, claiming to be only 90% fir as a result of his ear infection, going second with a 38.597, only to be demoted when Button goes quickest again (37.969).

Twenty-two minutes into the session, only Buemi, Bourdais, Vettel and Kovalainen haven't set times, though the German is on track.

At the top of the timesheets, Rosberg goes second, splitting the Brawns. As Vettel goes fifteenth, Glock has an off at Turn 4, a corner that has caught a few drivers out this weekend.

As Hamilton seeks to improve on eighteenth, the sky overhead is almost black. Elsewhere, Vettel improves to sixth with a 38.180.

A 37.811 sees Rosberg go quickest, as Kovalainen takes sixteenth with a 39.347. The McLarens clearly struggling this afternoon.

Vettel goes quickest with a 37.735, however, moments later, countryman Rosberg re-takes the top spot with a 37.490.

Hamilton improves to eighth with a 38.690, as Bourdais goes quickest in the first sector. The Frenchman eventually crosses the line at 38.759 t go eleventh, three places behind his teammate.

At 'half-time', it's: Rosberg, Vettel, Button, Hamilton, Barrichello, Nakajima, Webber, Buemi, Trulli and Alonso. Glock and Trulli have completed the most laps (11), while Kovalainen has only completed 4.

Raikkonen goes quickest in the first sector, as the McLaren crew are seen spraying some sort of substance onto the tyres of Hamilton's car (truth serum?).

Raikkonen improves to fourteenth, however he remains 1.36s off the pace of Rosberg. Next time around the 2007 champion goes second with a 37.494, just 0.004s off Rosberg's best.

A stunner of a lap sees Heidfeld go quickest with a 37.026, as Bridgestone and the FIA make enquiries into what the McLaren were doing with that spray. It's thought the Woking crew were trying to find a suspected puncture.

Nakajima, currently eighth, is told not to overdrive the car. The Williams driver responds by failing to improve.

Massa goes second with a 37.451, improving with a 37.162 next time around. However, all eyes are on Button who goes quickest in the second sector, finally crossing the line at 36.541 to go quickest. However, the Englishman reports that he has seen a large puff of white smoke coming out of the back of his car.