Ahead of today's opening practice session, the air temperature is 22 degrees C, while the track temperature is 28 degrees. It is bright and sunny. However, rain is forecast for both Saturday and Sunday.

Tyre options this weekend are soft (prime) and supersoft (option), while the DRS zone is just as the cars come on to the main straight after Rascasse/Anthony Noghes and, as in 2011, while the DRS can be used anywhere during the practice sessions and qualifying, its use in the tunnel is banned at all times.

For once, all the main drivers are on duty, with no test or reserve drivers in action, such is the unique challenge this circuit presents.

Kovalainen is first out when the lights go green, followed by Vergne - one of several drivers sporting new helmet livery, his being based on the legendary Jean Alesi's - Karthikeyan, Ricciardo and Petrov.

As expected, on returning to the pits Kovalainen reports that the track is "green" and "slippery".

Surprisingly, while the rest head back to the pits, their installation laps completed, Perez stays out, the Mexican posting the first time of the day (1:39.497). Seven minutes into the session all but Button have been out.

Almost fifteen minutes into the session, Button finally makes an appearance, the McLaren driver having the entire circuit to himself.

While the Caterhams sport QPR logos and Sauber the logos of Chelsea, at first glimpse it appears Lotus is paying tribute to one of the greatest football clubs of all, the cockerel of Tottenham Hotspur, but it's actually the team's new Angry Bird livery, the two having joined forces this weekend.

Button is moaning again, this time however, it is poor visibility that is getting the Englishman down.

At 1:07.55, as Perez reveals that his team made a routing brake change following his run, Vergne is the first driver out for a second run. The Frenchman crosses the line at 30.858. Elsewhere, Karthikeyan and Ricciardo head down the pitlane.

Vergne raises the benchmark with a 27.491 subsequently posting a 23.961 as he gets to grips with the track. Teammate Ricciardo goes second with a 27.617.

In the Lotus garage the mechanics are working furiously on Raikkonen's car, the Finn having voiced his unhappiness with its set up following his sole installation lap. Out on track, Vergne is down to 20.418, Ricciardo 21.171 and Karthikeyan 25.882.

With 56:00 on the clock, Grosjean, pic and Senna head down the pitlane, followed, shortly after, by Schumacher, who has a five-place grid penalty this weekend.

Sauber tweets that there are currently more drivers walking down the pitlane to the 'rest rooms' than are on track.

Schumacher goes third with a 19.941, the German having been given a thumbs up by team boss Ross Brawn yesterday. Moments later the Mercedes driver is demoted when Grosjean posts 19.905 to take third. Maldonado fifth ahead of Senna, Karthikeyan, Pic and Perez.

As Schumacher goes quickest (18.654), the director cuts to a great onboard shot from Grosjean's car, the car facing backwards at the Frenchman's right-front wheel. The Lotus driver responds by going quickest.

Maldonado improves to third (18.915), as Schumacher locks up going into Ste Devote, the German possibly distracted by Webber who exited the pits just ahead of him. Elsewhere, Karthikeyan is pushed back on track after taking to the escape road after locking up at Mirabeau.

Times continue to tumble, Grosjean remains quickest - now on 17.188 - ahead of Schumacher, Kobayashi, Maldonado, Vergne and Ricciardo.

At half-time, all but Glock, Raikkonen, Vettel, Webber, di Resta, Hamilton and Button have posted times.

Rosberg improves to third with a 17.750 as teammate Schumacher gets up close and personal with the Armco coming out of Casino. Massa complains of understeer as he posts 17.935 to go fourth.

Alonso goes sixth and Webber seventh as the McLaren duo finally come out to play. The Spaniard subsequently improves to third with a 17.600. Lotus reveals that work on Raikkonen's car is complete and that the Finn will be out shortly.