Ahead of today's opening session, the air temperature is 32 degrees C, while the track temperature is 43 degrees.

A number of reserve/test drivers are on duty today, Jules Bianchi is in for Paul di Resta, while Valtteri Bottas replaces Bruno Senna, Giedo van der Garde replaces Vitaly Petrov, Ma Qing Hua replaces Narain Karthikeyan and Max Chilton makes his debut courtesy of Charles Pic.

Tyre options this weekend are medium and soft, while, as in 2011, there are two DRS zones. That said, as we saw last weekend, and in 2011, double DRS zones usually don't work with all the hard work done in the first being undone in the second.

When the lights go green Raikkonen is first out of the box followed by Vergne, Ma, Grosjean, Glock, Chilton and Bianchi. Button, Webber and Vettel are among the early risers.

With both titles up for grabs there are numerous updates today, Ferrari having to break the official curfew when a number of components arrived fresh from Maranello in the early hours.

Kobayashi is one of the last to emerge, then he too comes out for an installation lap.

Twelve minutes into the session, Glock is the first driver to come out for a second run, the Marussia driver subsequently joined by his (temporary) teammate. The TV cameras pick up a chain of sensors on the rear of Chilton's car.

In the Force India garage Hulkenberg is told that there will be a delay while the team changes some wiring which will necessitate the removal of the bodywork. In the Ferrari garage Alonso is signing promotional postcards.

As Chilton posts 2:27.380, Ma heads down the pitlane in the HRT. The Chinese driver subsequently posts a 2:27.747. Last year's pole time was 1:38.481 so a long, long way to go.

As the session sinks into tedium, almost on the half hour, Vergne heads down the pitlane. Thankfully, the Frenchman ups the pace, crossing the line at a far more respectable 1:48.885. Vettel watches from the Red Bull garage. Next time around the Toro Rosso driver improves to 47.117.

Bottas, Maldonado and Perez get to work as the TV cameras pick up winglets that McLaren is testing with an eye on 2013.

Maldonado posts a 47.847 as Vergne improves with a 46.708. Moments later Bottas posts 47.308. In the McLaren garage Hamilton prepares to get to work.

As Bottas posts 46.085, Perez gets all crossed up but keeps it on the black stuff.

Raikkonen's first lap sees the Finn go sixth, as countryman Bottas goes quickest in all three sectors on his way to 45.602. Elsewhere, Hulkenberg and Schumacher run wide.

Bianchi goes second (46.221) as Raikkonen goes third and Massa fourth. Schumacher, who goes ninth, continues to struggle to stay on track.

In the Force Indias garage the mechanics continue to work on Hulkenberg's car, the German having complained of overheating.

No sooner has Massa gone second (46.048) than he is leapfrogged by Grosjean, Rosberg, Perez and then Bianchi (45.602).

A 45.309 sees Schumacher take the top spot, the German needing a decent result this weekend after a run of disappointing performances.

Alonso goes fourth with a 45.831 leaving Glock, Hulkenberg, Button, Vettel, Hamilton and Van der Garde as the only drivers yet to post a time. Next time around the Spaniard posts 45.099 having gone quickest in the first two sectors.

Vettel's first flying lap sees the German go eleventh (46.277) as Hamilton goes third with a 45.322.

Moments later Hamilton goes quickest (44.001) ahead of Vettel and Alonso, which sets us up nicely for the weekend. Long may it continue.

There's added spice in the form of Button, the Englishman going quickest in the first two sectors on his way to posting a 44.148 which puts him second. Teammate Hamilton responds with a 43.449.

The Force India crew having found what to do with all those nut and bolts and bits of wiring, Hulkenberg is now back on track, the German immediately improving to ninth.