Ahead of today's opening practice session the air temperature is 31 degrees C, while the track temperature is 35 degrees. It is 18:30 (local time) and humidity is 62%. While there is no chance of rain today we are expecting it on Saturday and Sunday.

The reason we say 18:30 is because emergency repairs are being carried out to the track at Turns 3 and 14. The repairs relate mainly to loose kerb stones following this morning's support event.

Article 31.5 of the Sporting Regulations dictates that there must be a minimum of two hours between sessions however, there is debate at to whether this one will be reduced to just one hour or the second session will be put back by thirty minutes.

Only one reserve driver is in action today, Narain Karthikeyan - who is to race in India next month - replacing Tonio Liuzzi.

Fifteen minutes into what should have been the session, the stewards announce that the kerbs have been removed at turn 3 and 14. They also confirm that drivers will not be penalised for crossing the white lines at these two corners.

They subsequently confirm that the session will be reduced to sixty minutes.

The lights go green and d'Ambrosio leads Alguersuari, Buemi and di Resta out on to the track. Within moments there are 19 cars on track, Glock an early spinner at Turn 7.

When Button leaves the pits, four minutes into the session, Vettel is the only driver yet to make an appearance. Moments later the world champion heads down the pitlane.

Ten minutes into the session, Rosberg is the first driver out for a second run, the German keen to make up for the disappointment of Monza and teammate Schumacher's improving form. Talking of whom, the seven-time champ is the second driver out for a second run.

As Rosberg posts the first time of the weekend (1:57.351), more and more drivers pour on to the track. Senna misses the chicane (Turn 10) as Schumacher posts 55.827 to go quickest.

A 59.340 sees Senna go third, watched by Vettel who impassively studies his monitor from the comfort of his cockpit.

Turn 10 is catching out a number of drivers, Adrian Sutil just one of them.

Barrichello complains about his brakes, one of a number of drivers encountering such a problem this circuit being particularly tough on them.

Webber goes quickest with a 52.869, ahead of Massa, di Resta, Sutil, Petrov, Schumacher and Kovalainen. Alonso and Vettel are both on track but no sign of the McLarens.

Massa goes quickest with a 52.043 as Sutil improves to third (53.748) and Alonso heads back to the pits.

Vettel goes third with a 53.252, the German sporting yet another helmet design. Alonso is wearing the same helmet he sported at Monaco.

Glock is holding up Webber, the Australian makes a move but the German closes the gap taking the Red Bull driver's right front wing off in the process. Both drivers return to the pits, the Virgin driver having suffered a puncture to his rear-left tyre in the process.

There more drama when flames leap from the front of Kovalainen's Lotus, his brakes having 'detonated'. The car stranded just off track, the session is red flagged.

At half-time, the order is: Massa, Webber, Vettel, Sutil, Alguersuari, Buemi, di Resta, Maldonado, Petrov and Senna.

The session resumes at 19:02, Trulli first out of the pitlane.

Great on board coverage with Alonso, the display on his steering wheel really showing up. Elsewhere, Rosberg complains that his visor is too dark.

Button, currently tenth, goes quickest in S1, maintaining the pace in S2. At the line the Englishman posts 50.952 to go quickest by over a second.

Schumacher is the latest to run wide at Turn 10, the German appearing to push just a little too hard. He's currently seventh (53.205).

Having gone quickest in the final two sectors, Vettel takes the top spot from Button, the German posting a 50.082.