Ahead of today's second session, the air temperature is 30 degrees C while the track temperature is 45 degrees. Humidity is 61 percent.

Lewis Hamilton topped the timesheets earlier, ahead of Vettel, Rosberg, Schumacher, Grosjean and Webber. Jenson Button was sidelined for much of the latter stages of the session with an oil leak, though the Woking team was eager to play this down.

Tyre options this weekend are hard and medium though we saw little of the softer rubber this morning. On the other hand, courtesy of the dusty track surface we saw plenty of drivers running wide.

Noticeably, both Mercedes looked strong, completing a good number of laps, while the Ferrari did its usual and used the session for testing purposes not fast times. Lotus also looked strong, both drivers making it into the top seven and lapping consistently.

Williams reserve driver Valtteri Bottas was in Bruno Senna's car this morning, as he will be on another fourteen occasions this season.

While rain was expected this afternoon, the radar shows that there are showers out there but are decreasing in size and also look set to miss the circuit. The threat of rain meant that this morning's was a particularly busy session, with drivers concentrating on longer runs.

The lights go green and Glock leads Karthikeyan and Pic on to the track to get proceedings underway.

Not convinced that the rain will stay away, more and more drivers pour on to the track, Alonso, Schumacher and Webber among them.

Glock posts the first time of the afternoon, the German crossing the line at 1:46.413. Moments later, Grosjean takes the top spot with a 43.554, only to be demoted by Webber's 41.144. Elsewhere, all manner of problems for de la Rosa, after a major lock-up he almost collects Perez as he leaves the pits.

Schumacher and then Vergne go quickest as the times tumble, Rosberg and Ricciardo almost instantly replacing them at the head of the table.

A 39.867 sees Schumacher retake the top spot as Button heads down the pitlane. Elsewhere, di Resta goes cross-country at Turn 15, the replay showing him to have a puncture to his right-front tyre.

Button goes fourth with a 40.317, ahead of Vergne, Rosberg and Webber as mechanics work on a problem on Vettel's car.

Hamilton posts 39.611 to go quickest as teammate flat-spots his tyres with a major lock-up. In the Force India garage the mechanics work on di Resta's car, the Scot having also suffered a problem with one of his brakes catching fire.

Schumacher takes to the grass at Turn 4, and runs wide again at Turn 6, the German very much on the limit. Mike Gascoyne tweets that his drivers are reporting a lot less grip than this morning.

Hamilton consolidates his top spot with a 38.921 as Button eases comfortably into second with a 39.754 only to be demoted when Alonso's 39.679 splits the Woking duo.

Just to convince the Woking boys that they won't be having it all their own way this weekend, on his first flying lap, Vettel bangs in a 39.624 to go second.

No sooner has Alonso goes second (39.391) than he is displaced by Vergne (39.297) and then Ricciardo, who displaces Hamilton also, the Australian crossing the line at 38.853. Both Toro Rosso drivers on mediums.

Webber is the first of the big guns to switch to the softer (medium) rubber, though it should be said that both Lotus drivers are also on this compound. Replay shows Webber and Kovalainen almost colliding as the Finn, on a flying lap, overtakes the Red Bull driver.

Currently eleventh (40.636), Webber posts a PB in S1 and another in S2. At the line the Red Bull driver posts 39.133 to go third. Elsewhere, Hamilton running wide in Turn 4.

Pirelli wants to know if it is easy to distinguish the silver (hard) and white (medium) tyres. In a word, no!

In the Sauber garage the rear end of Kobayashi's car is in pieces, the Japanese driver currently fifteenth (41.607), 2.754s off the pace. Mechanics in the Force India garage, working on di Resta's car, are equally busy.

Alonso (mediums) goes quickest in S2, finally crossing the line at 38.891 to go second. Massa and Vettel are also on the option rubber, the German making a mistake on his out lap on the softer rubber.