Ahead of today's sole free practice session, the air temperature is 21 degrees C, while the track temperature is 29 degrees. While there is a lot of cloud though it is understood that rain is not expected over the course of the hour.

While Robert Kubica and Nico Rosberg were quickest in yesterday's opening session, it was the McLarens that led the way in the second, though in all honesty everyone was compromised by the ever changing weather.

The locals will be delighted to have seen Mark Webber finish third quickest overall while Michael Schumacher was over 0.4s ahead of his Mercedes teammate.

Both Ferraris were off the pace but the Maranello team says there is absolutely no cause for concern as all should become clear as today develops.

Tyre compounds this weekend are hard (prime) and soft (option), and though we saw the softer compound in action yesterday the mixed weather conditions meant we were unable to get a true picture of how they performed. That said, it is understood that there is concern as to how long its takes the prime option to get up to optimal temperature.

While Lewis Hamilton has dominated the headlines for the last 24 hours, courtesy of his encounter with the local constabulary, it was Sauber which was really in the wars, particularly Kamui Kobayashi.

Meanwhile, as we report elsewhere, the Swiss team will not be using its version of the controversial K-duct system, admitting that it needs more time to develop the device.

The lights go green and Liuzzi leads the way ahead of Trulli, Kovalainen, Buemi, Kobayashi, Kubica and Petrov.

Four minutes into the session, Hamilton stops at the end of the pitlane to perform a (legal) burnout. His teammate lines up behind him.

Ten minutes into the session, with no times on the board, all but Webber and the Mercedes drivers have been out.

Petrov is the first driver to come out for a second run, followed, shortly afterwards, by de la Rosa, Massa and Glock.

Petrov runs wide at the penultimate corner on his out lap, thereby compromising his first flying lap. Nevertheless, he posts a 1:32.342 benchmark. Next time around the Russian crosses the line at 28.597.

Massa posts 28.516, having lost a lot of time in sector three, while de la Rosa goes third ahead of Glock.

Massa raises the benchmark with a 27.190 as the Mercedes duo finally get to work, leaving Webber as the only driver still to show.

Hulkenberg goes second and Vettel third (27.513) only to be demoted as Petrov takes second with a 27.244. Elsewhere, Webber heads down the pitlane.

Alonso slows down at the final corner in an attempt to get some clear track, something which is proving quite difficult this year - don't forget, we now have 24 cars as opposed to 20 - a factor that could be decisive in qualifying.

Vettel goes quickest (26.242) and Rosberg second, as Schumacher slips into fourth behind Massa. Webber posts 32.026 to ho nineteenth.

Having gone quickest in the first two sectors, Lewis Hamilton crosses the line at 25.706 to go quickest. Elsewhere, Alonso gets viciously 'cut up' by Senna, the Spaniard making his anger quite clear.

Schumacher posts 26.083 to go second, as attention shifts to Button who has yet to post a time. The Englishman crosses the line at 26.138 to go fourth.

Much to the delight of the partisan crowd, Webber goes quickest in the first sector and third, crossing the line at 25.774 to go second. Replay shows Senna getting in the way of Hulkenberg. However, moments later a number of drivers breathe a sigh of relief as the Brazilian parks his HRT by the side of the track at Turn 2.

At half-time, it's: Hamilton, Webber, Button, Vettel, Schumacher, Rosberg, Massa, Buemi, Hulkenberg and Kubica.

Kubica complains of a lack of "overall grip", claiming that his car is "sliding everywhere". A complaint that is no doubt being echoed in almost every other garage along the pitlane.

Petrov moves up to seventh with a 26.661, the Russian having completed the most laps at this stage (13). Massa, Buemi, Barrichello, Alguersuari, de la Rosa and Kovalainen are all on 10.

Alonso posts 25.916 to go third, the Ferrari star making the most of a relatively clear track.