Ahead of today's first free practice session, the air temperature is 21 degrees C, while the track temperature is 24 degrees C. there has been rain for much of the morning, and while it has now stopped the track remains damp and consequently the session has officially been declared wet.

The gig news this morning is that Kamui Kobayashi is standing in for Timo Glock today as the German is suffering from a very heavy cold and fever and has been advised to rest by the team's doctor.

The tyres available this weekend are hard (prime) and soft (option).

When the lights go green, it is Vettel who leads the way, followed by Heidfeld, Alguersuari, Buemi and Kubica.

Since the last Grand Prix here in 2006 there have been a number of changes, including: asphalt laid in parts of the run-off area around the outside of turns 1 and 2 and resurfacing of the track between turns 17 and 7.

With seven minutes of the session gone all but Barrichello have been out for an installation lap, however, as Button is halfway round the track the rain begins to fall again, albeit lightly. Nonetheless, shortly afterwards Barrichello comes out for his installation lap and during his lap the rain ceases just as promptly as it began.

Fifteen minutes into the session Kovalainen head down the pitlane followed shortly afterwards by his McLaren teammate.

The Finn posts 1:52.546 however, moments later, in the same conditions, his English teammate crosses the line at 49.730.

As Vettel and Grosjean join in the fun, Hamilton raises the benchmark with a 46.974 while Kovalainen remains over 2s off his pace. Vettel goes second with a 28.286.

A 47.702 sees Raikkonen go second as Buemi and Fisichella leave the pits. Its claimed that there will be further rain within the next twenty-five minutes.

Fisichella goes third, behind Hamilton and Raikkonen, with a 48.224, as Buemi goes fourth, ahead of Vettel and Kovalainen.

A big moment for Alonso who goes off into the gravel at the Hairpin, he is lucky to keep it out of the barriers. Though it is not raining the track remains quite damp. Elsewhere, teammate Grosjean goes second with a 47.072.

Next time around Alonso goes quickest, crossing the line at 46.152 despite a mistake at Spoon Curve.

No sooner has Grosjean gone second to make it a Renault 1-2 than Vettel posts 43.952 having gone quickest in all three sectors. Barrichello posts 45.747 to go third.

Next time around Vettel goes even quicker posting a 43.218, over 2s faster than second placed Alonso. Still no times from Heidfeld, Trulli, Liuzzi or Sutil, while rookie Kobayashi is sixteenth.

Hamilton closes to within 0.182s of Vettel as Button posts 44.969 to go third. Moments later however, the Englishman is demoted by Nakajima and then Webber.

At half-time, it's: Vettel, Hamilton, Webber, Nakajima, Button, Alonso, Barrichello, Grosjean, Alguersuari and Raikkonen.

Having gone quickest in all three sectors, Hamilton takes the top spot with a 42.642, elsewhere, Liuzzi goes eighth while teammate Sutil is now the only driver who hasn't posted a time.

Raikkonen goes fifth (43.691) only to be demotes when, from out of nowhere, Sutil produces a 43.055 to go second. The German was on his second flying lap.

A 42.591 sees Nakajima go quickest, the Japanese driver needing to do something special in the next couple of races if he is to stay in F1.

Kobayashi moves up to eighth with a 43.407 and promptly goes quickest in the first sector of his next lap. However, a mistake in the second sector sees him fail to improve again. However, next time around the Williams driver does raise the benchmark, crossing the line at 42.591.

Fisichella goes third with a 42.853 having gone quickest in the second sector.

With twenty minutes remaining, and large parts of the track clearly drying, Kovalainen posts 42.495 to go quickest, however, this is almost instantly eclipsed by Sutil who posts 41.958.