Ahead of today's opening session the air temperature is 19 degrees C, while the track temperature is 19 degrees.

Tyre choices this weekend are hard and medium whilst the two DRS zones are on the main straight and on the shorter back straight between Turns 9 and 10.

As ever, being the first race of the European season, Barcelona will see upgrades from every team even though Fernando Alonso was playing this down during yesterday's significantly downbeat press conference.

Various drivers and teams are bigging up rivals chances but at present it looks as though Mercedes are the clear pace-setters ahead of Red Bull and Ferrari. McLaren and Williams will both be looking for a major improvement this weekend, though the downforce requirement here are likely to further frustrate the Woking outfit.

Unusually, there has been no-preseason testing here, so, other than simulator work, the teams head into the weekend with the very basics in terms of baseline. Which, in addition to the extra set of tyres for the first half hour, should mean a little bit more action.

There are two reserve drivers in action this morning, Felipe Nasr replacing Valtteri Bottas at Williams and Giedo Van der Garde replacing Esteban Gutierrez at Sauber.

The lights go green and Ericsson leads Hulkenberg, Kvyat, Magnussen, Massa and Bianchi on to the circuit.

As more and more cars take to the track one can almost hear Wagner's Ride of the Valkyries, the air being thick with the smell of flo-vis.

In minutes all but Button have been out, the rear of Raikkonen's Ferrari absolutely smothered in yellow flo-vis.

Kvyat posts the first time of the weekend, the ever-improving Russian crossing the line at 1:36.471. Elsewhere, Button heads down the pitlane.

As Kvyat heads back to the pits the track falls silent, all the drivers remain stoically in their garages.

Thankfully, after a few minutes an engine fires up and Bianchi, Van der Garde, Maldonado and Button head down the pitlane. In time more drivers follow.

A 34.069 sees Maldonado go quickest but this is soon beaten by Button who posts 30.717. Magnussen's subsequent 30.300 makes it a McLaren 1-2.

Despite an unusually untidy lap, Alonso goes quickest (29.974) as the camera picks up on Perez who is struggling to control his car after his (left) mirror became loose and fell into the cockpit. Steering with one hand on the wheel and the other holding the errant mirror, which is in danger of getting trapped in the gap between the steering wheel and the cockpit side, he heads back to the pits.

Ominously, on his first flying lap, Rosberg posts 29.623, while Hulkenberg goes second ahead of Massa and Alonso. Moments later however the Spaniard retakes the top spot with a 28.770 before losing out to Hamilton and his 28.028.

Twenty-five minutes into the session it's game over for Vettel - currently fourteenth on 30.942 - who stops coming out of T5. The German gets out of his car and helps the marshals push it to safety. This, of course, is the much talked about new chassis - or rather the one used in pre-season testing. Surely not the one that kept stopping and catching fire.

No such problems for teammate Ricciardo who posts 28.775 to go third behind the Mercedes duo, albeit 0.727s off Hamilton's pace. Raikkonen improves to fifth.

Having been significantly quick in the first two sectors, Hamilton dives into the pits, the Mercedes driver confident that he has much more in reserve.

On the half hour, the teams now having to give back that extra set of tyres, the circuit once again falls silent.

At this point, it's: Hamilton, Rosberg, Ricciardo, Alonso, Button, Raikkonen, Nasr, Hulkenberg, Massa and Sutil.