Ahead of today's opening free practice session, the air temperature is 19 degrees and the track temperature is 21 degrees. As expected it is overcast with worrying dark clouds hovering overhead. While it is not raining, it is widely thought that there will be a downpour before the session ends.

A welcome visitor to the Interlagos paddock is Felipe Massa, who looks delighted to be back, albeit as a spectator.

The lights go green and within the first two minutes of the session all but local hero Rubens Barrichello have been out.

Kubica, Heidfeld and Button complete two installation laps, the Brawn featuring a number of news sponsors not least Brazilian brewer Cervejaria Petropolis.

After a brief pit stop Button is back on track, the Englishman clearly keen to get some baseline data in the bag for what is a critical weekend for him.

Alguersuari posts the first time of the weekend, the Spaniard crossing the line at 1:24.099. Next time around the Toro Rosso drivers posts a 20.385 only to be eclipsed by teammate Buemi with a 18.382.

As the Toro Rosso duo continue, Buemi raising the benchmark with a 14.689, Raikkonen is the first of the big guns to come out. As the Finn heads down the pitlane, sixteen minutes into the session, he is followed by Heikki Kovalainen.

On his first flying lap Raikkonen goes third with a 15.836 as Kovalainen goes fourth with a 17.555.

Mindful of the rain that appears imminent, more and more drivers take to the track including Kamui Kobayashi who is standing in for Timo Glock.

A 14.021 sees Raikkonen go quickest, as Buemi remains second ahead of Barrichello, Webber and Kovalainen.

All but Buemi, Alguersuari, Fisichella and Grosjean are on track when, twenty-three minutes into the session, the rain begins to fall. It's not too hard, but the mass of black clouds in the distance suggest that there is plenty more to come.

Webber goes quickest with a 13.951 as Hamilton posts 14.727 to go fifth. Next time around, the Englishman, making full use of his KERS, takes the top spot with a 13.631.

The tyre options this weekend are medium (prime) and super-soft (option), though we're unlikely to see much of the options today.

While a number of drivers are clearly struggling it is Alonso who is first to enjoy an off-track experience as the rain falls that little bit harder. Moments later Kobayashi has a similar experience.

Having gone quickest in the first sector, Barrichello goes second overall, crossing the line at 13.549. Teammate, and championship rival, Button is fourth (13.572).

Webber does well to avoid a collision with former teammate Nakajima, the Japanese driver appearing to be daydreaming.

Much to the delight of the hardy souls in the stands, Barrichello goes quickest with a 13.121, the Brazilian knowing that this is his last real chance of championship glory. Elsewhere, Grosjean makes full use of the generous run-off areas.

From out of nowhere Vettel produces a 12.932 to go quickest. The German has barely crossed the line when the rain really begins to fall. Everyone heads back to the pits.

After a few minutes of total inactivity Alguersuari breaks the deadlock, the Spaniard heading down the pitlane on a set of inters. A lap later the Toro Rosso driver is back in the pits.

After another couple of minutes of silence, Kovalainen heads down the pitlane. He is joined, shortly afterwards, by Grosjean.

The Finn's first lap is around 3s off the pace, however, next time around he's a lot quicker, tempting more drivers to go out and join him. As the Finn improves from nineteenth to fourteenth with a 14.258, Grosjean takes a detour which sees him demolish one of the polystyrene brake markers at Juncao. With polystyrene all over the track the red flag is brought out in order that it can be cleared away.

As the most hi-tech sport on the plant bides grinds to a halt, a dozen or so marshals slowly make their way to the scene of the incident. Armed with nothing more than brooms they get to work, seemingly oblivious to the fact that twenty of the fastest men on earth want to get back to work. It's farcical, comical but actually quite endearing, typically Latin.