Ahead of today's sole free practices session, the air temperature is 24 degrees C, while the track temperature is 26 degrees. It is somewhat overcast.

While McLaren topped the timesheets in both of yesterday's sessions, it is widely felt that Red Bull was holding back. That said, while Mark Webber suffered an engine failure - expected according to the team - teammate Sebastian Vettel wasn't entirely happy with the newly introduced F-duct and as a result the team won't be using it for the remainder of the weekend.

Other than McLaren and Red Bull, both Mercedes looked fairly good, as did the Renault. For Ferrari, celebrating its 800th Formula One World Championship Grand Prix this weekend, Fernando Alonso had the edge.

Tyre options this weekend are hard (prime) and soft (option). The soft tyres only appeared in the second session yesterday, and in most cases were only good for one really hot lap.

When the lights go green the Lotus duo lead a gaggle of twelve cars out on to the track. However, within moments Kovalainen is complaining of a problem with his gearbox. He is told to return to the pits and remain in third gear.

Another driver having problems is Sutil who, having crawled his way round the track, grinds to a halt just after entering the pitlane, appearing to have suffered a major hydraulics issue.

Nine minutes into the session, all but the Mercedes and Webber have been out. Kovalainen's problem has been traced to a faulty sensor as opposed to a faulty gearbox.

Thirteen minutes into the session, di Grassi is the first driver to come out for a second run, followed, moments later, by Chandhok.

As di Grassi posts a 33.802, Mark Webber, on his first lap of the day, is running very, very slowly. The engine is still running, however, the look on the faces of the Red Bull crew on the pit-wall says it all. Moments later, it is revealed that the Webber is suffering a throttle issue.

Alguersuari goes quickest with a 29.700, ahead of di Grassi, Chandhok and Glock. Still no sign of the Mercedes duo.

As Webber continues to wind his way back to the pits, seemingly in first gear, teammate Vettel goes second with a 29.793 to Alguersuari's 29.539.

A 29.482 sees Kubica go quickest as the Mercedes finally come out to play. Buemi makes it a Toro Rosso 2-3 with a 29.741.

Having gone quickest in all three sectors, Vettel goes quickest with a 28.011. Alonso goes tenth and Massa fifteenth, however, next time around the Brazilian improves to third with a 29.006.

No sooner has Rosberg posted 28.851 to go second than his teammate crosses the line at 28.295. Moments later, Alonso crosses the line at 27.866 while Hamilton goes third with a 28.103.

As Button begin his first flying lap of the day, teammate Hamilton improves with a 27.827 and Vettel raises the benchmark ever higher (27.482).

Button posts 28.274 to go fifth, as Schumacher posts personal bests in the first two sectors, finally crossing the line at 27.879 to take fourth.

A massive spin for Hamilton at Turn 8 after the Englishman runs wide just after the second apex. The McLaren spins 360 and slides off into the gravel. At first it appears that he's beached it, however, he is able to get going again, albeit with two punctures. Elsewhere, Button goes quickest overall in the first sector, but is unable to maintain the pace.

Just after half-time, it's: Vettel, Hamilton, Alonso, Schumacher, Button, Kubica, Massa, de la Rosa, Rosberg and Petrov.

With twenty-five minutes remaining, Webber heads back down the pitlane, his throttle issue hopefully resolved. The Australian, like Sutil, has yet to post a time.

Rosberg improves to seventh with a 28.617, but remains 0.8s off his teammate's pace.

On his first flying lap of the day, Webber posts 29.376 to go fourteenth, as Force India reveals that it won't be able to get Sutil back on track this session.

Next time around Webber posts 28.334 to go seventh, still 0.852s off his teammate's pace.

With seventeen minutes remaining, Webber posts 27.807 to make it a Red Bull 1-2, the Milton Keynes outfit finally beginning to show its hand.