Ahead of today's opening free practice session, the air temperature is 22 degrees C, while the track temperature is 30 degrees. It is bright and sunny and expected to remain like this for the rest of the weekend.

The lights go green and Timo Glock leads the way, followed by Karthikeyan, Chandhok, Alguersuari and local hero Kamui Kobayashi.

Five minutes into the session all but Petrov have been out, the McLarens, in particular, sporting massive rear wings.

The front wing on Massa's Ferrari is virtually yellow such is the amount of flow-vis paint it is covered in.

Eighteen minutes in, with Petrov yet to show, Button is the first driver to come out for a second run. As he returns to the pits he is replaced by Karthikeyan and Ricciardo. Petrov is running the 'traditional' bodywork on the R31 while teammate Senna has the 'tighter' version.

Twenty-three minutes into the session, as Petrov finally heads down the pitlane, Karthikeyan posts 1:49.408 and Ricciardo 46.073. Next time around the Spaniard improves to 43.544 and the Indian 44.733.

On his first flying lap Kobayashi goes quickest with a 39.445 subsequently improving with a 38.921. Teammate Perez goes second with a 41.435. The Sauber duo enjoying lots of upgrades this weekend.

As more and more drivers pour on to the track, Webber goes quickest (36.194), ahead of Massa and Kobayashi, however, the Australian is subsequently eclipsed by Hamilton and then Alonso (35.181).

Hamilton improves with a 34.427 but Alonso ups the ante with a 34.372, with Senna and Petrov now the only drivers yet to post a time.

Crawling around the back end of the circuit very slowly, Maldonado eventually pulls off to the side of the track after running wide.

Having gone quickest in all three sectors, Hamilton re-takes the top spot with a 33.725. Alguersuari posts 34.937 to go third, ahead of Webber, Massa, Buemi and Schumacher.

As Senna goes seventeenth with a 40.491, Button goes quickest overall with a 33.648.

Vettel improves to fourth with a 34.375, the onboard camera picking up the fact that the German takes 130R with his DRS open.