Ahead of today's opening practice session, the air temperature is 21 degrees C and the track temperature is 22 degrees. It is overcast and unseasonably cool.

Tyre options this weekend are the same as in Monaco - soft and supersoft - though it is highly unlikely that we will see the same sort of pit strategy on Sunday.

Not for the first time, the weather look likely to play a part in this weekend's proceedings, and while this morning's session is likely to be dry, rain is forecast for this afternoon and much of the rest of the weekend.

All twenty-four drivers are on duty this morning, no reserve or test drivers called into action.

With the FIA having clarified the rules regarding the holes in the floor of the Red Bull, the Milton Keynes has made the necessary modifications.

The lights go green and Vergne leads the way, followed by Kovalainen, Ricciardo, Raikkonen, Grosjean, Karthikeyan, Kobayashi, Hamilton and Webber.

Some rank stupidity from Pic who appears to be racing Alonso, the Spaniard, quite rightly, clearly frustrated by the Frenchman's silliness. Both Ferraris are absolutely plastered in flo-vis paint. Both Red Bulls, on the other hand, are sporting some very odd looking sensoring devices.

Ten minutes into the session, after several minutes of total inactivity, both Lotus are back on track. As is Perez.

Grosjean posts 1:20.295 and Raikkonen 20.347, while Perez can only manage a 25.205 on his first timed lap.

Next time around Raikkonen ups the ante with an 18.703 while Perez, who didn't race here last year, posts 21.773.

With an eye on the clouds more and more drivers take to the track. Vergne goes third (20.770), ahead of Perez and Kobayashi while Button pits following a second installation lap.

A 17.386 sees Grosjean retake the top spot only to be eclipsed by his teammate's 17.188 moment later. Rosberg goes sixth and Alonso ninth. Elsewhere, having already cut the final chicane, Senna goes cross-country at Turn 9.

Rosberg goes quickest with a 16.837 and teammate Schumacher ninth (19.454).

Twenty-five minutes into the session, with 17 names on the timesheets, di Resta complains of moisture on his visor. As cars continue to miss the final chicane, the first few drops of rain are reported.

Having gone second (17.035), Hamilton goes quickest in S1 and S2 on his next lap, finally crossing the line at 16.080 to go quickest.

Schumacher improves to fourth and Massa fifth, as Kovalainen is another driver enjoying a spot of cross-country. Massa subsequently posts a 16.619 to go third.

Webber's first flying lap sees the Australian go nineteenth (20.314), as Pic, Button, Glock and Vettel remain the only drivers yet to post a time.

As Webber improves to twelfth (17.671), teammate Vettel posts a 21.169 to go twentieth.

Sporting an impressive new rear wing, Maldonado goes tenth with a 17.180.

Replay shows a fox lucky not to be hit by a Lotus as it runs across the track.

Vettel improves to fourth as teammate Webber goes quickest in S1. The Monaco winner subsequently posts a 16.347 to go third.

In the Ferrari garage the mechanics are working on the rear of Massa's car, the Brazilian running a new exhaust exit very similar to that found on the McLaren.

As Perez almost hits the wall at the final chicane, Senna outbrakes himself at Turn 3 and end up stuck in the escape road for a while before being able to recover.

Mercedes looking good as Schumacher goes third (16.310).

At half-time, it's: Hamilton, Rosberg, Schumacher, Webber, Vettel, Kobayashi, Massa, Perez, Button and Grosjean. All but Glock have posted times.