Ahead of today's second practice session the air temperature is 19 degrees C, while the track temperature is 19 degrees. It stopped raining shortly after the first session and since then the track had begun to dry. However, minutes before this session was due to get underway it began raining again… albeit lightly. Nonetheless, the session is declared wet and therefore most drivers will begin on Inters.

The lights go green and Alguersuari leads the way, followed by Buemi, Kovalainen, Trulli, d'Ambrosio, Ricciardo, Maldonado, Kobayashi and a whole load of others.

As more and more drivers leave the pits, and mindful of the lack of running earlier, not to mention the fear of the current downpour intensifying, drivers look set to get in a few laps from the outset. All but Hamilton, Massa, Schumacher and Perez are on track as Alguersuari posts 2:00.067, though the Englishman has at least completed an installation lap.

Just five minutes into the session there are thirteen names on the timesheets with Vettel leading the way (1:56.604), ahead of Webber, Alonso and Alguersuari.

Next time around it is Button who goes quickest (54.447) as Alonso complains about the rain only to be told that it "should be constant". So that's alright then.

As Sutil goes quickest in S1, Vettel having just gone quickest overall (54.340), Button complains of lack of grip at the front.

A 54.063 sees Buemi go quickest, the appearance of Jean-Eric Vergne in the opening session clearly a wake-up call for the Swiss and Jaime Alguersuari, that's if Daniel Ricciardo isn't already keeping them on their toes.

Hamilton posts a 52.659 to make it a McLaren 1-2, his teammate having just posted a 52.664. Vettel is now third ahead of Buemi, Webber and Rosberg. Schumacher has finally left the pits.

Button goes quickest in all three sectors, finally crossing the line at 51.798. Elsewhere, Alonso runs out of track at Turn 11 and takes to the escape road.

Schumacher goes tenth with a 55.161 as Hamilton raises the bar with a 51.189. The rain now appears to have stopped.

As Maldonado improves to seventeenth, replays show both Massa and Barrichello running wide as they struggle for grip.

With Saturday and Sunday expected to be dry, teams are in a bit of a quandary in terms of what they want to do today.

Alguersuari posts a 50.932 to go fourth as Button dives into the pits having just gone quickest in S1.

Having asked where he's losing time, Hamilton is told the "middle sector", the Englishman still quickest, 0.104s ahead of his teammate.

Bruno Senna - sporting a helmet the bears the years of his uncle's three titles - shows no such skills as he runs out of road.

A dry line now emerging, certainly on some parts of the track, Alonso improves to third with a 52.774. Still not right for dry tyres however.

With half an hour remaining we're in a sort of limbo. While not dry enough for dry tyres, times on the Inters are not improving.

Rosberg pulls to the side of the track the German having clumped Alguersuari who had just come out of the pits. His front wing trapped underneath his car, and his wheel askew, the session is over for the Mercedes driver. The Toro Rosso has also picked up some damage though he is able to return to the pits. Ironically, the Spaniard was the first driver to switch to dry tyres.

There is a piece of debris in the middle of the corner following the Rosberg incident, but nobody appears to be doing anything about it. Eventually a steward runs out and kicks it away.

Drivers continue to run wide, Webber and Hamilton amongst them, the Australian appearing to have been avoiding some debris. Alonso spins at Turn 10.

Senna runs wide and loses control on the wet kerbing causing the Renault to spin 360.

Buemi is on dry tyres, the Swiss immediately having a spin, his teammate leaves the Toro Rosso garage also on the supersoft rubber. As Buemi gets going again the car is horribly twitchy.