Ahead of today's opening practice session, the air temperature is 17 degrees C, while the track temperature is 19 degrees.

There are two DRS zones this weekend. The detection point of the first is 150 metres after Turn 10, with the activation point 320m after Turn 11, while the second zone's detection point is 65m after Turn 18, with the activation point 80m after Turn 20, on the start/finish straight.

Tyre choices are medium (prime) and soft (option). Following a rain shower the session has been declared wet, even though the track looks relatively dry, and consequently a couple of cars are sporting Inters.

For those of you have been on Mars for the last week, only 18 drivers are contesting this weekend's race, Marussia and Caterham both having gone into administration since the previous race.

Max Verstappen is making his second appearance today, the youngster replacing Jean-Eric Vergne, whilst Felipe Nasr is in Valtteri Bottas' Williams.

Romain Grosjean's Lotus is sporting a new nose for this session, in fact, unlike the version on Pastor Maldonado's car, it is a 'traditional' nose.

The lights go green and Perez is first out, followed by Hulkenberg, Verstappen and Nasr.

Raikkonen's Ferrari is sporting a strange looking sensor that goes over the bulkhead section of his cockpit. The Maranello outfit has already admitted that it will be running a number of 2015 components this weekend, and we don't feel they'll be the only ones.

Clearly keen to get down to business, Hamilton and Rosberg post the first times of the weekend, the Briton crossing the line at 1:49.164. He and his teammate are both on primes.

Sutil is the third driver to post a time, the German stopping the clock at 52.050.

After a couple of slow laps Hamilton ups the ante and goes for it, as does Rosberg who posts 46.317. The Briton, losing time in traffic, posts 43.547 to go second to Button who has just posted 43.245.

As Button improves with a 41.772, Nasr goes third (44.650), ahead of Rosberg, Magnussen, Massa and Verstappen.

As Massa improves with a 42.865, so too does Magnussen who posts 42.348 to make it a McLaren 1-2.

As Alonso locks-up in T13, Ricciardo goes third overall with a 42.598.

Asked about his car's balance, Ricciardo lists a number of issues before ending with the line... "generally not awful".

Alonso splits the McLarens with a 41.323, the Spaniard's plans for 2015 still the subject of much speculation. Moments later, Magnussen posts 41.078 to demote the Ferrari driver to third.

Grosjean runs wide at T8 as Alonso also has a moment running over the damp artificial grass and throwing up a cloud of spray.

As the opening half hour comes to an end, after which the extra set of tyres must be handed back, Magnussen is quickest, ahead of Button, Alonso, Hamilton, Raikkonen, Rosberg, Nasr, Kvyat, Massa and Ricciardo.

As Vettel posts 43.261 to go 12th, countryman Hulkenberg remains the only driver yet to post a time.

Button locks-up and runs wide at T12.

With 45:00 remaining, only Magnussen and Verstappen are on track, though they are subsequently joined by Hulkenberg.

Red Bull reveals that an ERS issue has side-lined Ricciardo for the rest of the session. The Austrian outfit is already the subject of much discussion as Vettel looks unlikely to take part in qualifying as the team is looking to change his entire power unit.

Despite going wide in T20, Rosberg posts 41.690 to go sixth. Elsewhere, Hulkenberg complains that he is not happy with his brake balance.

Having improved to fourth, Vettel is back in the pits. Back on track Rosberg goes second with a 40.675 only to be demoted when teammate, and title rival, Hamilton posts 40.016.

Without the 'protection' of Caterham and Marussia, Lotus is propping up the timesheet, both drivers over 3.2s off the pace.