Ahead of today's all-important qualifying session, the air temperature is 22 degrees C, whilst the track temperature is 36 degrees.

The track temperature is significantly down on yesterday, however, tomorrow it is due to rise again.

While Nico Rosberg led the way in both of yesterday's sessions, this morning, it was teammate Lewis Hamilton who topped the timesheets.

The Briton admitted yesterday that he was off the pace, his car "all over the place", leading to suggestions that he was looking ahead to another difficult weekend as in Austria.

It hasn't been plain sailing for Rosberg either however, the German losing track time in FP1 with a hydraulics issue and further (option) running this morning with a suspected gearbox oil leak.

All that aside however, the Mercedes look to be the absolute class of the field here and certain for a dominant win.

Though the Ferraris were second and third, neither driver has looked comfortable, and in their efforts to keep pace with the Mercedes we could well see one (or both) fall foul of the track limit rules in this session.

In fact, after three practice sessions it is the Toro Rosso duo that looks strong, both drivers continually near the top of the timesheets. Whether their form can be maintained this afternoon and tomorrow however remains to be seen.

Williams is looking strong, as is the B-spec Force India, indeed, all the Mercedes runners must feel might confident this weekend.

Other than McLaren, the biggest disappointment thus far is Sauber, which is clearly struggling. Then again, it's struggles are nothing compared to the Woking outfit, where it is feared Fernando Alonso will miss this afternoon's session.

To add to the fun, Charlie Whiting has warned that any driver running wide at T9 (Copse) will have their time deleted.

The lights go green and the Manor duo are first out. Hamilton is another early riser.

In no time at all, all bar Vettel, Grosjean and the Saubers are on track, all on the prime (hard) rubber.

Hamilton's first lap is a 34.009, while Bottas posts 34.476. Moment later however, Rosberg crosses the line at 33.654.

Hulkenberg runs wide at T9 which means his time is deleted before he's even posted it.

Alonso is not only on track, he passes teammate Button on the run to the Maggots complex.

As the Mercedes duo trade fastest sectors, Vettel runs wide in T9. Teammate Raikkonen goes fourth (34.496). Elsewhere, a spin for Verstappen.

Rosberg improves to 33.475 and Hamilton to 33.796 as Vettel's time is deleted, as is that of Perez.

Stevens is unhappy at sharing the same piece of tarmac as his teammate, "it's pretty stupid running us so close," he claims.

On the option rubber, Alonso goes tenth with a 35.329.

Never mind 'Ctrl' and 'Alt', it's 'Del' only for Verstappen.

Vettel goes fifth with a 34.347, but it's unclear whether that's a delated time or what. Time (no pun intended) will tell.

The highest placed option runner is Ericsson (35.294), who is currently tenth.

The Force India duo switch to options, As do the Lotus duo and Verstappen.

Ericsson is told that due to the number of drivers having their times deleted he is with a chance of making it to Q2. At which point Maldonado's time is scrubbed.

Kvyat goes fifth (34.314) but having gone off at T9 will his time also be deleted. Indeed it is, he is demoted to thirteenth.

Maldonado, Button, Nasr and the Manors in the drop zone, with Alonso, Ericsson and Kvyat hovering.

Strangely, Raikkonen is back on track on options.

A late improvement to 14th for Alonso, but he is demoted by Nasr as Raikkonen goes quickest (33.426).

Ericsson posts 34.643 to go twelfth, and thereby demotes Alonso to the drop zone.

Vettel (options) goes third with a 33.562.

Quickest is Raikkonen, ahead of Rosberg, Vettel, Hamilton, Bottas, Perez, Ricciardo, Kvyat, Massa and Hulkenberg.

We lose Nasr, Alonso, Button, Stevens and Merhi. Merhi made a late improvement but had crossed the infamous track limit at T9 and therefore had his time deleted. He would still have missed the cut but would have been closer to his teammate.