Ahead of today's opening session the air temperature is 19 degrees C, while the track temperature is 32 degrees C. It is bright and sunny... and, yes... this is Britain.

For today's sessions, in light of last weekend's problems, Valtteri Bottas has taken on a new power unit - his third of the season - as the Austrian unit is returned to base for further checks.

There are no reserve drivers on duty.

One of the main points of interest today - other than Zak Brown facing the media at the FIA press conference later - is the addition of a third DRS zone and in particular the fact that drivers will be able to use DRS in the fast corners 1 and 2.

Speaking yesterday, Lewis Hamilton suggested that Max Verstappen will be first to try it flat-out, while Sebastian Vettel believes it will further divide the field as only the better-funded outfit will have the necessary downforce.

Ericsson is first out, followed by Magnussen, Vandoorne and Gasly.

As McLaren seeks to find the root of its aero issues (amongst others), Alonso heads out sports a garden gate sensor.

Vettel is among the early risers.

Bottas is about to head out when the Finn is told to stop and the car pushed back into its garage. Mercedes understandably cautious in the wake of last weekend's failure.

Five minutes in and all but the Mercedes duo and Verstappen have appeared. A good mixture of hards, mediums and softs thus far.

Ricciardo also has a large sensor device fitted to his car, Red Bull understood to be running back-to-back rear wing tests.

Bottas finally heads out.

"It's really bumpy," warns Stroll.

Leclerc enquire why the stop slot outside the garage is at an angle.

Verstappen heads out, leaving Hamilton as the only no-show, the Briton clearly determined to get the home crowd waiting in feverish anticipation.

Hartley posts the first time of the weekend, the Toro Rosso drivers crossing the line at 1:35.079. Shortly after, Verstappen posts 30.863 and Gasly 35.537.

Perez posts the fourth time of the morning, the Force India driver stopping the clock at 31.671.

The cameras pick up on Verstappen predictably running through T1 (Abbey) with his DRS flap wide open. The Red Bull driver is on mediums, while the three other drivers to have posted times were on softs.

As Raikkonen posts 30.480, Verstappen improves to 30.009.

Hamilton heads out and at the end of an exploratory lap heads back to the pits again.

Vettel posts 30.386 to go second only to be demoted when his teammate improves with a 30.110.

Sirotkin is off and in the gravel at T17. However, he is able to continue. Despite catching the slide at the start, the Russian is unable to do anything about the snap of oversteer.

A 30.271 sees Ocon go third, ahead of Vettel, Perez, Grosjean and Ricciardo.

Bottas posts 30.384 to go fourth.

Ricciardo, on the hards, improves to fourth with a 30.319.

Vettel goes quickest with a 29.244, and while Bottas is quickest in the first two sectors a poor final sector sees him post 29.841 to go fourth.

"I can't open the DRS in T1," says Sainz.

Hamilton's first lap is a conservative 41.651, next time around he looks set to improve before aborting the lap.

Now Hamilton goes quickest in S1, following up with a PB in S2. At the line he posts 29.757 to go fifth. He's on mediums.

Hulkenberg is advised to close DRS manually before T1 then remain flat-out, he can manually re-open it.

"This is the bumpiest track I've ever been on," reports Hamilton.

Bumps or no bumps he subsequently improves to 28.908.

A little silliness involving Magnussen and Alonso, the Spaniard claiming that the Dane tried to "hit me two times" - note to Doors fans, not Love me two times - "very dangerous driving," adds the Spaniard.

At the 40 minute point where the extra set of tyres have to be handed back to Pirelli, the order is: Hamilton, Vettel, Verstappen, Raikkonen, Bottas, Ricciardo, Ocon, Grosjean, Perez and Magnussen.

The leading five are on mediums - as are the Haas duo, while Ricciardo is on hards and Ocon and Perez are on softs.

Following the usual lull, Gasly is the first out as the session resumes.

Now on softs, Bottas goes quickest in all three sectors finally crossing the line at 28.143.

Alonso is the only driver yet to post a time, While Sirotkin is 5s off the pace, with Hulkenberg, Gasly and Ericsson not doing much better.

Now Hamilton, also on softs, goes quickest in S1, only managing a PB is S2. Another PB in S3 sees the Briton improve to 28.153, just 0.010s off his teammate's best.

PBs in all three sectors sees Magnussen improve to ninth (30.158), though he is somewhat greedy in terms of the run-off at the final corner.

As Bottas consolidates his top spot with a 28.854, Grosjean posts 29.352 to go fifth. The Frenchman clearly looking to pick up where he left off in Austria.

Moments later however, the VSC is deployed as Grosjean spins off and clouts the barrier at T2. Blaming "the bump" and his failure to hit the DRS button, when asked the condition of the car he responds "it is destroyed". It isn't but there is quite a bit of damage to the left-front.

Shortly before his off, the Haas driver was demoted to sixth when Ricciardo improves to fourth (29.162) on the softs.

Ricciardo subsequently splits the Mercedes pair with a 28.144 but Hamilton is already on a hot lap. The Briton bangs in a 27.487 despite only being quickest in S1.

PBs in all three sectors see Raikkonen improve to fourth (28.218) only to be demoted when Vettel goes third with a 27.998.

Raikkonen is off at T6 and on the grass (don't go there), it takes an age for the Finn to get going again. Replay shows the Ferrari driver spinning and going off backwards, taking a mighty pounding as his car goes over the bumps. Elsewhere a minor off for Ricciardo.

Looking set to post his first time of the day, Alonso aborts the lap following a mistake in S2 which sees him run wide.

The Spaniard subsequently posts a 31.842, he's 4.355s off the pace but it's a start.

Verstappen is back on track, the Red Bull driver yet to try the softs.

Despite sticking with the mediums and running wide in the final corner, Verstappen improves his time (28.325) but remains sixth.

As Alonso improves to 19th with a 30.847, Verstappen slows on the pit straight.

"Do not shift, do not shift," the Red Bull driver is told as he slows and parks the car. Not the best start for the Milton-Keynes based outfit.

The VSC is deployed as the car is pushed to safety.

Moments later the chequered flag is waved as the session comes to an end.

Hamilton is quickest, ahead of Bottas, Vettel, Ricciardo, Raikkonen, Verstappen, Grosjean, Perez, Ocon and Stroll.

Ericsson is eleventh, ahead of Gasly, Leclerc, Magnussen, Alonso, Sainz, Vandoorne, Hulkenberg, Hartley and Sirotkin.

Check out our Friday gallery from Silverstone, here.