Ahead of today's opening session, the air temperature is 18 degrees C, while the track temperature is 21 degrees. As widely predicted, the skies are grey and there has been overnight rain which has left the track with a few damp patches.

With it hardly being used during the year the track is already green, the damp conditions, not to mention that slippery wet grass ensure that unless they are especially wary one or two drivers could be up close and personal with the barriers over the next ninety minutes.

Tyre choice this weekend is soft (prime) and supersoft (option) , a combination last seen in Canada.

As previously reported, Bruno Senna is in Nick Heidfeld's car for this session, while Nico Hulkenberg is in Jarno Trulli's Force India.

The lights go green and Ricciardo leads the way, followed by Glock, Liuzzi, d'Ambrosio, Alguersuari and Petrov.

Five minutes into the session, all but Button have been out, the Englishman needing a good result here after consecutive DNFs in Britain and Germany.

Earlier there was a photo shoot down at Ferrari, Fernando Alonso celebrating his thirtieth birthday, complete with birthday cake. Unfortunately, the candles on the cake set off the smoke alarms.

Massa, is the first driver to come out for a second run, the Brazilian returning to the scene of his horrendous accident in 2009.

According to the Italian team, Massa is making a series of out-ins, making regular changes to his front wing as the team continues its usual Friday aerodynamic development programme.

Eighteen minutes into the session, despite the fact that Massa has completed 5 laps, Hulkenberg is the first driver to post a time, the German crossing the line at 1:31.073. Next time around the Force India improves to 29.671.

More and more drivers are following Massa's example, doing a lap, returning for a practice pit stop/start or adjustment then straight back out again.

As Hulkenberg posts 28.286, Buemi, who faces a five-place grid penalty following his clash with Heidfeld in Germany, goes second with a 28.584.

Celebrating his 200th Grand Prix, Button goes third with a 27.748 as Buemi goes quickest in S1. The vortices from the rear wing on the McLaren indicate how damp the air is.

Next time around Button goes quickest (25.697) as Ricciardo goes fourth (35.799). Moments later a 28.574 sees Hamilton go fourth.

The big question this weekend, after two races which Red Bull hasn't won, indeed Germany, where Sebastian Vettel didn't make it to the podium, all eyes are on the Austrian team this weekend. If McLaren and Ferrari continue to take a bite out of Red Bull's lead it will set us up nicely for the second half of the season.

Button ups the ante with a 24.983, but Hamilton is already on a very quick lap, going quickest in the first two sectors. The 2008 world champion finally crosses the line at 24.284.

As Massa goes third (25.312), Ferrari reports that there could be a minor rain shower coming up. Birthday boy Alonso posts 27.073 to go seventh.

Having gone quickest in S3, Alonso takes the top spot with a 24.179 as Webber heads down the pitlane. With ideal conditions predicted for Saturday and Sunday some drivers might feel that there is no need for serious running today.

As the cameras pick up Alonso making a mistake and running wide in Turn 4, Massa goes quickest in S2, improving to third overall (24.291).

On his first flying lap, Webber goes thirteenth (30.953), the Australian lifting off as he hits a wet patch.

Alonso improves to 23.642, his teammate to 24.115 and Webber takes ninth with a 26.580.

As Vettel finally comes out to play, one of six drivers yet to post a time, teammate Webber posts 23.666 to go second.

At half-time, it's: Alonso, Webber, Massa, Hamilton, Button, Schumacher, Kobayashi, Rosberg, di Resta and Perez.