Ahead of today's sole free practice session, the air temperature is 21 degrees C, while the track temperature is 26 degrees. It is cooler than yesterday and slightly overcast. Furthermore, the wind is picking up.

While the top nineteen drivers were covered by just 1.097s yesterday, the sessions were largely inconclusive. McLaren has clearly made a major step forward but it remains to be seen where they truly stand in comparison to Red Bull and Brawn.

Of the title protagonists, Button and Brawn appeared to be having a harder time of it that the Red Bull duo, the Englishman appearing to struggle just a little even though - tyre-wise - conditions this weekend should be perfect for him.

The driver really suffering however was Felipe Massa, who appeared to spend more time off track than on it.

Of the two tyre options available - soft and super-soft - the super-soft appeared to have the edge.

Hopefully, we will glean a little more regarding the true state of play over the next hour.

The lights go green and Fisichella leads the way, followed by Trulli, Vettel, Buemi and Glock. With a couple of minutes all bar Barrichello are on track.

While the majority of drivers head back to their pits after the obligatory installation lap, Hamilton completes two laps, as does Heidfeld. Barrichello goes out for his installation lap also.

There follows a period of total inactivity until, eleven minutes into the session, Trulli heads down the pitlane, followed, shortly afterwards, by his Toyota teammate.

Trulli working hard in order to generate heat into his tyres as more and more cars pour on to the track.

The Italian crosses the line at 1:30.122 to set the benchmark, however, this is almost instantly beaten by his teammate who posts 25.815. Alguersuari goes second, splitting the Toyotas with a 29.048.

Alonso goes quickest (25.577) as Rosberg goes second, ahead of Glock and Trulli. Alguersuari improves to fourth as Glock complains of a problem with his hydraulics.

A 24.473 sees Rosberg go quickest ahead of Buemi as Raikkonen begins his first flying lap of the day. Alonso goes second as Rosberg improves with a 23.659.

Buemi takes the top spot with a 23.633 but is soon eclipsed by Rosberg (23.443) who is looking very good this weekend. The German is said to be in talks with BMW regarding a seat in 2010.

McLaren is back on top as Kovalainen posts a 23.343, the Finn making the most of all the upgrades he didn't have in Germany plus a couple of others. Fellow-Finn Raikkonen improves to fourth.

Coming up to half-time, Buemi re-takes the top spot with a 23.123, however, it doesn't last for long as Kovalainen is the first driver to break the 1:22 barrier.

As Hamilton complains of 'bottoming', the reigning World Champion goes quickest with a 22.280, making it a McLaren 1-2.

Barrichello goes fourth and Button sixth as Webber holds tenth and Vettel thirteenth.

Webber improves to sixth with a 23.222 right behind the two Brawns. Elsewhere, Massa improves to tenth.

At half-time, it's: Hamilton, Kubica, Kovalainen, Buemi, Massa, Button, Barrichello, Webber, Sutil and Rosberg.

Alguersuari appears to be one of the first drivers to switch to the super-softs. The Spanish youngster goes eleventh (3.500) as Glock's session appears to be over, the German now standing on the pit-wall as his crew work on that hydraulics problem.

A 22.652 sees Alguersuari go second 0.372s off Hamilton's pace. Teammate Buemi is currently fifth.

As Alonso (super-softs) goes quickest in the middle sector, Rosberg goes third overall. However, the German is demoted when the Renault driver goes second with a 22.369.

Both Brawns improves, Barrichello to fifth and Button to sixth, as more and more drivers switch to the super-softs.