Ahead of today's opening free practice session the air temperature is 20 degrees C, whilst the track temperature is 23 degrees. It is somewhat overcast with a twenty percent chance of rain.

This weekend, for the first time this year, we have the supersofts on duty, while the prime rubber is soft.

There is a single DRS zone, with the detection point located 80m after Turn 16 and the activation point located 18m after Turn 19.

The track has been resurfaced from the exit of the Casino until the start of the tunnel, while small sections before the Nouvelle Chicane and Tabac (Turn 12) have been resurfaced.

With an eye on the unforgiving nature of this circuit, not to mention the extra time needed to fix this year's car, there are no reserve drivers on duty this morning.

That said, Lewis Hamilton is very late in arriving. Turning up by boat (natch) after trying to enter the Red Bull Energy Station he then runs - accompanied by his minders - to the Mercedes garage. Now all he has to do is change into his overalls.

Gutierrez is first out, followed by Magnussen, Vergne, Maldonado, Alonso, Ericsson, Sutil and Bottas. After last year's tribute helmet to Francois Cevert worn by Jean-Eric Vergne, Ericsson is sporting a Ronnie Peterson helmet.

Chilton is very nearly an early casualty, the Marussia driver carrying too much speed into Rascasse and almost hitting the barriers. Despite the soft rubber at their disposal the drivers are sure to be struggling for grip this weekend, a situation not helped when you have a car as unwieldy as the Marussia.

After a few minutes all but Grosjean and Hamilton have been out. Vettel's car is smothered in flo-vis, the Red Bulls sporting double monkey seats.

Rosberg posts the first time of the weekend, the German crossing the line at 1:24.681. Winner here last year, Rosberg is keen to bring his teammate's winning streak to an end.

As he improves to 22.534 he is advised that his right-front brake is cold whilst his left-front is hot.

As his teammate ups the ante with a 21.070, Hamilton heads down the pitlane, the world championship leader having (obviously) found his helmet and overalls. Ericsson posts 35.105 to go second (of two).

As Rosberg consolidates his top spot with a 20.094 and Hamilton goes second (25.332), Bernie Ecclestone arrives by boat.

Hamilton has a big moment at the chicane, the Mercedes drivers almost collecting Kvyat. Indeed, Sutil, Perez, Ricciardo and Maldonado all have moments at the chicane.

After just twenty minutes there are seventeen times on the doors, Rosberg, heads Hamilton, Ricciardo, Perez, Button, Hulkenberg, Alonso, Massa, Sutil and Magnussen.

A 19.912 sees Ricciardo go quickest as Chilton spins at Mirabeau The Briton is stuck on track, facing the wrong way, for some time before being removed.

Rosberg is back on track, the German having the luxury of a clear track. Until he is joined by his teammate.

Both Mercedes drivers are pushing hard, Rosberg improving with an 18.970 and Hamilton an 18.973, the Briton really riding the kerbs.