Ahead of today's second free practice session, the air temperature is 28 degrees C while the track temperature is 31 degrees. Humidity is 45%.

Sebastian Vettel was quickest this morning, ahead of Hamilton, Button and Webber. However, other than the fact that it was a fairly typical Friday session, the track was damp for much of the session following a deluge in the hour before it got underway. To add to the excitement, further rain is expected over the weekend.

While the track has now dried, parts of the Williams pitlane remain damp especially outside the Williams garage.

The lights go green and di Grassi leads the way followed by Klien. Kobayashi is back in the second Lotus after handing it over to Fairuz Fauzy in the opening session.

As Heidfeld posts a 1:45.314, Hamilton, Button, Massa, Alonso, Vettel and Webber head down the pitlane. Indeed, all but Kubica, Petrov, Alguersuari and Kobayashi are on track.

Hamilton goes straight to the top of the timesheets on his first flying lap, the McLaren driver crossing the line at 43.292. Moments later Button goes second ahead of Heidfeld and Massa.

No sooner has Barrichello gone fifth (44.947) than Alonso goes quickest overall, the Spaniard posting a 42.474 on his first flying lap. Button improves to second with a 43.049.

"I've got massive front locking," complains Button as the onboard camera does indeed show him locking up in Turn 6. Meanwhile, teammate Hamilton re-takes the top spot with a 41.664 ahead of Alonso and Massa. The Red Bull duo are back in the pits, neither driver having posted a time.

Having gone quickest in S2, Alonso goes quickest overall, the Spaniard crossing the line at 41.473. The Ferrari looking very stable, certainly compared to the McLaren.

Webber goes sixth with a 42.892 as teammate Vettel heads down the pitlane. While Webber improves with a 42.438, Vettel posts 43.523 to go fifteenth.

Kobayashi and Kubica both improve however, it is Vettel who makes the biggest leap, the German posting a 42.705, thereby moving up to sixth. Next time around the Red Bull driver improves again, this time with a 42.367. That said, he teammate responds with a 42.082 to go third.

Unlike the first session, when only the first two drivers were within a second of one another, this time around the top eight - Alonso, Hamilton, Kubica, Webber, Massa, Button, Schumacher and Vettel are covered by 0.894s.

As the sun slowly sets the impressive trackside lighting kicks in. The air temperature has now dropped to 27 degrees C and the track temperature 30 degrees.

Hamilton has a worrying moments as he gets caught up behind a slowing Senna. The Englishman, dives into the pits crossing the track right in front of the Hispania. The stewards subsequently announce that they are to investigate the incident.

With an eye on Sunday, the drivers are now on longer runs. We've yet to see anyone make the switch to the option (super-soft) tyres.

Vettel improves to second with a 41.534, the German just 0.070s off Alonso's pace.

The quickest of the newbies (Glock) is still over 2s off the pace of the slowest of the established runners (Buemi). These three teams need to make a significant improvement over the winter.

Alonso is the first of the big guns to go out on the softer tyres, as Massa and Hamilton also make the switch. The Brazilian goes quickest in the first sector but it is Hamilton who goes quickest overall, the McLaren driver stopping the clock at 41.213.

Alguersuari spins at Turn 19 and subsequently stalls. Disgusted with himself, the Spaniard climbs from his car and slowly walks back to the pits. A number of other drivers are equally disgusted having had their laps running by the subsequent yellow flags.

Hamilton improves again consolidating his top spot with a 40.888. In the best Hollywood tradition the four title protagonists fill the first four places on the timesheets.

Alonso complains of massive oversteer; "I don't know what I can do," he moans.

With 22:10 on the clock Massa pulls to the side of the track on the back straight that leads to Turn 11. He climbs from the Ferrari which is pushed to safety.