Ahead of today's opening practice session, the first free practice session of the 2009 Formula One World Championship, the air temperature is 18 degrees C, while the track temperature is 25 degrees. It's unseasonably cool, and overcast.

The pitlane light goes green, and like last year it is the Force Indias that lead the way, followed by Robert Kubica. The Pole is not running with KERS this weekend, whereas his teammate, Nick Heidfeld, is.

Piquet, Trulli, Bourdais, Buemi, Webber, Vettel, Rosberg and Nakajima are among the others eager to get out and complete an installation lap.

As Raikkonen, Hamilton, Glock and Button take to the track, all but Kovalainen, Alonso and Barrichello haven't appeared.

Eight minutes into the session, all but Alonso and Barrichello have been out. Their installation laps completed, the rest of the drivers are out of their cars as the mechanics get to work.

With just four engines available for these practice sessions this year, teams will want to limit their running. On the other hand, because there is no in-season testing, this is the only opportunity for the teams to try out those all-important upgrades.

Vettel, sporting a rather severe haircut, talks to Helmut Marko in the Red Bull garage, while Lewis Hamilton chats to Ron Dennis at McLaren. At Renault, Nelson Piquet Snr talks to Flavio Briatore.

Twenty-four minutes into the session, Rubens Barrichello heads down the pitlane in the Brawn, the Brazilian veteran about to embark on his seventeenth F1 season.

Buemi is the first driver to come out for a second run, the Swiss rookie really throwing his Toro Rosso around. He continues around and posts the first flying lap of the weekend, indeed the year, crossing the line at 1:41.493. Next time around he gets down to 36.659.

As Buemi continues, getting down to a 35.296, he is eventually joined by Kimi Raikkonen. On his first flying lap, the 2007 champion goes quickest with a 32.121, at which point Alonso heads down the pitlane. Rosberg is also on track.

As Alonso dives into the pits, Raikkonen improves with a 29.513. Elsewhere, Massa and Hamilton leave the pits.

Raikkonen, now down to 28.718, locks up and cuts across the grass at Turn 1, as Rosberg goes third with a 34.330.

A 31.735 sees Heidfeld go quickest, as Massa, looking very aggressive, gets it all wrong, locks up and heads off up an escape road.

Trulli goes third (31.589) and Hamilton sixth (32.910), as Button begins his first flying lap. Button goes seventh with a 31.060, as Hamilton improves to fourth (30.590).

A 29.772 sees Massa go second, 1.314s off his teammate's pace, as Heidfeld goes third ahead of Rosberg, Trulli and Hamilton.

As Button goes second with a 28.641, Vettel's session appears to be over before it has hardly begun. The German pulls to the side of the track with a hydraulic pressure problem.

At half-time, it's: Raikkonen, Button, Massa, Heidfeld, Rosberg, Trulli, Nakajima, Hamilton, Webber and Kovalainen.

As Kovalainen gets out of shape, Barrichello goes fourth (29.683), however, the Brazilian is almost instantly demoted to eighth as a whole flurry of drivers go quicker, most notably Rosberg, who goes second, and Kovalainen, who goes fourth.

A 27.982 sees Kovalainen go quickest, as Button takes fourth with a 28.641. Sutil and Alonso are the only drivers yet to post a time.

Barrichello takes the top spot with a 27.743, as Sutil goes fifteenth with a 30.498. Timo Glock goes third in the Toyota with a 8.418.

Fifty-five minutes into the session, Alonso is in his car and finally heads out on to the track.

The two tyre options this weekend are super-soft and medium, which we will refer to as soft and medium. Raikkonen is the first driver to use the soft option and immediately goes quickest with a 6.750. However, his next lap isn't as good, indeed, he backs off.

A 30.338 sees Alonso go seventeenth, just behind his Brazilian teammate who has completed 7 laps more.