Ahead of today's opening practice session, the air temperature is 27 degrees C, while the track temperature is 41 degrees.

Romain Grosjean is in Bruno Senna's Renault for this session, while Jean-Eric Vergne is in Sebastien Buemi's Toro Rosso and Robert Wickens is in Jerome d'Ambrosio's Virgin.

Tyre options this weekend are medium (prime) and soft (option). This being the circuit where Pirelli's return to F1 got underway in earnest last year when all the teams took part in a mammoth test following the Grand Prix.

The teams have been given two extra sets of an experimental soft compound tyre for use during today's sessions so we should - fingers crossed - witness a bit more action.

When the lights go green, Alguersuari leads the way, followed by Liuzzi, Vergne, Perez and Kovalainen. World champion Sebastian Vettel among the early risers - the German having very fond memories of this track.

While most return to the pits after a single installation lap, Perez stays out and completes two.

Seven minutes into the session everyone has been out, Rosberg and Schumacher, like Perez, completing two laps.

Vergne, Perez and Grosjean are the first drivers out for a second run, the two Frenchman back in action here next week during the Young Driver Test.

Grosjean crosses the line at 1:50.375 to get the weekend underway. Moments later Hamilton heads down the pitlane, his McLaren shod with the experimental tyres.

No sooner has Grosjean improved to 46.067 than Hamilton crosses the line at 43.899. Liuzzi posts 52.536 and Ricciardo 53.095.

As Kovalainen runs wide, Barrichello arks his car at the side of the track just after Turn 13, his session over before it has begun. Replay shows that the Brazilian suffered a sudden loss of power, "oil pressure", he tells his team. Elsewhere, Hamilton improves to 42.617.

Maldonado - who has a ten place grid penalty this weekend for using up his engine allocation - goes second with a 45.44, ahead of Kovalainen, Grosjean, Alguersuari and Massa (46.082).

Hamilton improves with a 41.846 as Maldonado consolidates second (44.623) and Massa goes fourth (44.978).

Vettel goes fifth, Schumacher seventh, Webber tenth and Petrov thirteenth on their first laps, as Hamilton continues with the experimental tyres.

Approaching half-time, Vettel goes second (42.701), ahead of Alonso, Button and Webber, the timesheet taking on its usual appearance.

Indeed, it's business as usual when Webber goes quickest and Red Bull teammate Vettel second, the Australian posting a 41.692.

Button ups the ante with a 40.955 as Kobayashi and Glock remain the only drivers yet to post a time. And Barrichello of course.

Rosberg goes sixth with a 42.498, subsequently improving with a 421.130 to go fifth.

A number of drivers other than Hamilton have run with the experimental tyres, which, as Ferrari admits, makes comparisons impossible.

As Barrichello's car arrives back at the Williams garage, Maldonado heads out to improve on seventh (43.255).

Hamilton re-takes the top spot with a 40.466 to make it a McLaren 1-2, Webber and Vettel now third and fourth. Rosberg is fifth, ahead of Alonso, Maldonado, Schumacher, Alguersuari and Sutil.

Williams reveals that Barrichello's engine has suffered a "catastrophic failure". However, with an engine in hand the Brazilian will not incur a penalty - providing, of course, that there are no further failures.

A big spin for Massa at Turn 1, the back end of the car inexplicably snapping out. Rob Smedley's reaction on the pit-wall suggests driver error.

A minute or so later, Alonso has a similar moment between Turns 5 and 6. The car appears to be 'beached' on the kerbs, but the Spaniard is able to continue. Elsewhere, Kovalainen in all manner of trouble with a Lotus that appears unwilling to go where he wants it to.