Ahead of the start of today's first practice session, the air temperature is 27 degrees C, while the track temperature is 28 degrees. Humidity, much as expected, is 84%, while it is fairly overcast.

Tyre options this weekend are hard (prime) and soft (option) however, the teams have each been given two extra sets of experimental hard tyres today.

The DRS activation zone sees drivers free to use their movable rear wings coming out of Turn 15 on to the main straight - providing they were within one second of the car ahead at the designated spot going into that corner.

Hulkenberg is in di Resta's Force India for this session, while Ricciardo is in Buemi's Toro Rosso and Valsecchi is in Kovalainen's Lotus.

The lights go green and Trulli leads the way, followed by D'Ambrosio, Perez, Alguersuari, Hulkenberg and Karthikeyan. Hispania's other driver, Tonio Liuzzi is another 'early riser', both drivers feeling very confident now that the team's front wing has been approved. Certainly, the fact that both cars are running this early in the session appears promising.

One by one the drivers come out for their installation laps, and five minutes into the session all but Button and Schumacher have been out. That said, moments later the Englishman and German head down the pitlane as Trulli and Ricciardo come out for a second run, as does Rosberg.

Thirteen minutes into the session Hulkenberg heads down the pitlane and, having completed another installation lap, looks set to post the first flying lap of the weekend. Sure enough the German posts a 1:44.557, watched by Paul di Resta from the pit-wall. Next time around the Force India reserve driver posts 42.475.

Further misery for Hispania as smoke pours from the back of Karthikeyan's car, indeed, it began even as the Indian pulled out of his garage. As he pulls to the side of the track several corner later, a weary voice over the radio urges the Indian to turn his engine off.

Maldonado is the second name on the timesheets, the Venezuelan crossing the line at 45.332.

As Heidfeld posts 42.285, Alonso and Massa are both on track, as are the McLaren duo.

Heidfeld raises the benchmark with a 40.823, while Hulkenberg improves with a 41.096.

Having gone quickest in S1, Heidfeld locks up going into a corner however, the wheel doesn't unlock and as the German heads back to the pits - his wheel still 'frozen' - a thick cloud of rubber smoke and brake dust pours from the car.

Schumacher goes third (41.169) with his first flying lap, ahead of Maldonado, Perez, Valsecchi and Liuzzi. In the Renault garage mechanics and Pirelli people swarm over Heidfeld's car.

Thirty-two minutes into the session, Maldonado posts a 40.854 to go second as Rosberg goes seventh with a 42.286.

Vettel leaves the pits for his first proper run, the German looking to take his fourth successive win this weekend. Elsewhere, Alguersuari goes second with a 40.770. Heidfeld remains quickest.

As Vettel goes tenth (44.004), replay shows Maldonado locking up his left-front. Next time around the world champion improves with a 42.901 but remains tenth. Almost unseen, Webber has gone seventh with a 41.545.

Having gone quickest in the two final sectors, Webber goes quickest overall, the Australian posting a 39.870. Elsewhere, Trulli sheds some bodywork, Button goes seventh with a 40.927 and Karthikeyan's Hispania is pushed back up the pitlane.

Webber improves with a 39.448 increasing the gap to his teammate to 2.408s. Rosberg leapfrogs his Mercedes teammate with a 40.861 to take fifth.

At half-time, it's: Webber, Heidfeld, Alguersuari, Maldonado, Rosberg, Schumacher, Button, Hulkenberg, Sutil and Ricciardo.

Hamilton goes quickest in the final sector and second overall, the McLaren driver crossing the line at 39.747. Next time around the Englishman closes to within 0.36s of Webber.