Ahead of today's opening practice session the air temperature is 15 degrees C, whilst the track temperature is 23 degrees. It is bright but there is a fair amount of cloud. The track is still a little damp from overnight rain and it is anticipated that there could be further downpours later today and tomorrow. Indeed, there is a 20% chance of rain later in this session.

Tyres available this weekend, for the third race running, are soft (prime) and supersoft (option). There are two DRS zones, one on the main pit straight and the other between turns 2 and 3.

A number of drivers are expected to take grid penalties this weekend, most notably Fernando Alonso and the Red Bull duo.

Honda has 'updated' the power unit in the Spaniard's car, whilst McLaren has also brought a number of updates for the Spaniard including a revised nose and front and rear wings.

With the next races at Silverstone and the Hungaroring more suited to the RB11, Red Bull is likely to take its power unit penalty here, though one has the feeling that there might be more to follow.

There is only one reserve driver on duty this morning, Jolyon Palmer replacing Romain Grosjean at Lotus.

The lights go green and Kvyat is first out, his car sporting a sensor that resembles the old fashioned TV aerial, followed by Ericsson and Raikkonen, the Finn hopefully having calmed down following his outburst at yesterday's (Ferrari) press conference.

Less than five minutes in and all but Hamilton, Vettel and Merhi have made an appearance.

Ominously, at the end of his install lap, Alonso coats into an down the pitlane, the Spaniard reporting that his engine stopped coming out of T8. A number of McLaren mechanics run to assist him but he is able to make it back to his garage... his engine silent.

Back in his garage, Alonso is out of his car, top unbuttoned and shades on. A dreadful start for the Spaniard and his team.

A close up reveals that many of the sensors on the Red Bull are taped on.

With Alonso side-lined, will McLaren fit the various updates to Button's car.

Fifteen minutes in and Nasr posts the first time of the weekend, the Brazilian stopping the clock at 1:18.021. Best time in FP1 last year was Rosberg's 1:11.295.

Bottas posts 16.162 as Nasr improves with a 17.181. Shortly after, Massa posts a far more sensible 14.969.

Moran and more drivers pour on to the track, Rosberg ups the ante with a 12.791.

Honda reveals that whilst the unit in Alonso's car was his fifth, the problem might not be as bad as it looks. Fingers crossed.

A 13.001 sees Hamilton go second, ahead of Massa, Bottas, Maldonado and Raikkonen.

Maldonado runs wide in T8 and Perez T1, T8 under close scrutiny from Charlie Whiting last year when it was felt drivers were gaining an advantage by using all the track... and then some.

As Rosberg improves to 11.389, Raikkonen posts 12.112 to go second.

Oh dear, problems for Vettel, the German pulling off track between turns 1 and 2, smoke billowing from his front brakes. Vettel climbs from the car which is lifted on to a truck for a speedy return to the pits.

Back on track, Rosberg has improved to 10.401, ahead of Hamilton, Raikkonen, Kvyat and Maldonado.

Woah! A near miss in the pitlane as Ferrari team boss Maurizio Arrivabene walks towards his garage totally unaware of Massa's Williams thundering towards him. The Brazilian screams to a halt and Arrivabene signals a sigh of relief... and apology.

The opening half hour comes to a close, Rosberg quickest, ahead of Hamilton, Raikkonen, Kvyat, Maldonado, Massa, Perez, Bottas, Verstappen and Ricciardo. Alonso is the only driver who hasn't posted a time.

As has become the norm, following the opening half hour when drivers have a 'free' set of tyres, there follows a long period of total inactivity... other than a typically Italian, highly excitable recovery of Vettel's car from the low-loader.

After a ten-minute lull an engine finally fires up, it's Nasr. For several minutes the Brazilian has the track to himself, until he is eventually joined by his Sauber teammate.