Ahead of today's opening session, the air temperature is 13 degrees C, while the track temperature is 20 degrees. It's bright and sunny, but exceedingly cool.

While it is at the next race, when the European season gets underway, that teams will begin introducing serious updates, a number of teams are introducing new parts this weekend. Although the FIA has sent out a clear warning regarding ride height devices, Ferrari is following the example set by McLaren and Sauber and running its own version of the F-duct today.

For Force India, Paul di Resta is driving Tonio Liuzzi's car in this session, while the tyre options are hard (prime) and soft (option)

The lights go green and di Resta leads the way followed by Trulli, who seems very keen to get past the Scot. Buemi, Kovalainen, de la Rosa, Alguersuari, Chandhok and Senna are also quick to go out.

While the other drivers complete an installation lap and head back to the pits, di Resta stays out on track and completes a second lap.

Five minutes into the session, all but Schumacher have been out. In the Mercedes garage the crew is working on the German's car.

Hamilton is the first driver to post a time (1:41.819), the Englishman appearing to get caught out by the extra speed provided by his F-duct at the end of the back straight.

After more than ten minutes of inactivity, Chandhok heads down the pitlane, followed, shortly afterwards, by di Grassi. The Indian's first time lap is a disappointing 50.913 as Senna, Glock, Petrov, Alonso and Rosberg get back to work. Alonso is understood to be the only Ferrari driver running the F-duct today.

Senna posts 44.840 to go second, ahead of Petrov, Chandhok and Glock. However, next time around, the Renault driver goes quickest with a 41.714.

di Resta goes quickest with a 40.551, almost immediately eclipsed by Petrov (39.516), while in the Virgin garage the mechanic check the front wing on Glock's car, the left-hand side having been damaged after going over a bump on the approach to Turn 1.

As di Resta goes quickest again (39.101), Schumacher finally leaves the Mercedes garage. de la Rosa goes third with a 39.377, ahead of Alguersuari, Kobayashi, Hamilton and Chandhok.

Alguersuari posts 38.504 to go quickest, as Kubica goes third with a 38.975 ahead of Massa (39.112).

Massa posts 38.360 to go quickest, but is almost instantly demoted when Kubica crosses the line at 37.899. Elsewhere, Hamilton goes quickest in the first two sectors, finally crossing the line at 37.536 to go quickest. Moments later, in his first flying lap, teammate Jenson Button goes second with a 37.832.

Next time around, Button goes quickest with a 37.008, raising the benchmark by a further 0.528.

At half-time, it's: Button, Hamilton, Kubica, Massa, Alguersuari, Vettel, de la Rosa, di Resta, Kobayashi and Petrov. No times, as yet, from Buemi, Sutil, Webber, Alonso, Rosberg or Schumacher.

A 36.775 sees Hamilton close to within 0.098s of his teammate, as Alonso grinds to a halt in the middle of the track just after Turn 6. Despite his team's assurances that engine reliability is not an issue, the thick blue smoke from the back of the car, followed by flames from the exhaust, very much suggest that this is exactly the case. The Spaniard walks disconsolately back to the pits.

Rosberg goes third (37.595) and Schumacher fifth (37.902) as Senna gets it all wrong at Turn 1, as does Sutil a few moments later.

A marshal removes bits of carbon fibre from the track, where it appears one of the Louts' has hit that notorious bump on the approach to Turn 1, damaging its diffuser.

Schumacher improves to fourth (37.809), ahead of Vettel, Kubica and Webber.

Petrov posts 37.745 to split the Mercedes, as Buemi remains the only driver - other than Alonso - to post a time.

With twenty minutes remaining, Vettel posts a personal best in the first sector as he seeks to improve on fourth (37.601).

A 36.748 sees Rosberg go second, splitting the McLarens., as Buemi finally posts a time (40.108) to go seventeenth.