Ahead of today's opening session, the air temperature is 15.5 degrees C, while the track temperature is 20.7 degrees. Following the heat of Barcelona, F1 crashes back to the reality of the Ardennes. Indeed, there is a 10% chance of rain... and 80% on Sunday.

Irony of ironies, Leclerc is warning that the SF1000 will struggle on Spa's numerous fast stretches, his comments coming one year after Ferrari began to turn its season around with what proved to be a controversial engine upgrade.

Sainz is first out, followed by Albon, with Raikkonen and Magnussen next to head out.

It might be cool, but judging by the flags above the pits there is almost no wind.

Due to the uncertainty of the weather, not to mention those fast sections, the teams are using this session very much for testing purposes, and other than the obligatory flo-via and aero rakes a number of teams are trying different aero packages not only for this weekend but looking ahead to Monza and beyond and even 2021.

As more drivers head out there is a mixture of all three compounds.

2019 winner, Leclerc is the first driver to post a time, crossing the line at 1:47.152. The youngster complains that his tyre temperature read out-out is wrong and asks what he can do about it. "Keep pushing," he is helpfully told. He subsequently improves to 14.033.

Ten minutes in and while Leclerc's is the only name on the board, Vettel, Verstappen, Hamilton and Bottas are the only drivers still to appear.

Being his 31st birthday today, the Finn is probably enjoying some celebratory porridge.

Leclerc heads back to his garage and silence falls over the track.

Following almost ten minutes of inactivity, Verstappen breaks the deadlock and heads out on a set of hards. Moments later, Norris follows, on mediums.

"Front end feels very strong," reports Verstappen, as Grosjean complains: "Sick engine, I've got no power".

Verstappen posts 45.886 and Norris 46.619, as Perez heads out on softs.

Kvyat is the fourth driver to post a time, the Russian crossing the line at 47.617.

The low downforce rear wing that Ferrari is trying looks like a TV dinner tray.

Straight out of the box, Bottas goes second with a 46.239. Moments later, Hamilton posts 45.988, both Mercedes drivers on the mediums.

A big lock-up for Norris in T1 as he looks to avoid a very slow AlphaTauri.

After 30 minutes, Verstappen remains quickest, ahead of Bottas, Hamilton, Norris, Perez, Gasly, Kvyat, Ricciardo, Ocon and Leclerc.

"What the **** is Norris doing," enquires Gasly, after encountering an unusually slow McLaren, "for **** sake!"

Not a great start for Haas, following Grosjean's power problems, both cars are up on their stands in the garage with the KERS warning signs in place.

"Our run plan is fairly normal today," reveals Renault, "with an added focus on the soft tyre, as the compounds are a step softer from last year. The rear wings on the cars have not been raced this year and are targeted towards the low downforce demands that Spa offers."

"Latifi..." Leclerc is told, as his engineer prepares to give him the current times. "Tell me only the drivers who are quick," responds the Ferrari driver.

Bottas improves to 45.664, but remains 0.194s off Verstappen's pace.

Stroll goes third with a 45.710, but is demoted when Hamilton stops the clock at 45.298.

"Your slow laps need to be a bit faster than this," Hamilton is told.

Haas reveals that the engine is being changed on Magnussen's car and the Dane will not be out again. The Dane has completed just one lap and hasn't posted a time.

As the time comes when the drivers have to hand back a set of tyres, it remains: Hamilton, Verstappen, Bottas, Stroll, Perez, Norris, Kvyat, Gasly, Albon and Ricciardo.

At which point Haas confirms that Grosjean's engine is being changed also, though it is understood the Frenchman's issue is not the same as his teammate's.

Eventually Norris gets things going again, the McLaren driver heading out on a brand new set of softs.

As Sainz heads out, Norris crosses the line at 45.274 to go quickest by 0.024s.

As Sainz begins his first flying lap he is warned that his "DRS issue in ongoing", but that he is to still use it.

Albon and Ricciardo head out, both on fresh softs as Sainz goes quickest (45.222).

As more and more drivers head out on the red-banded rubber, Albon goes quickest in S2, subsequently crossing the line at 45.075 to go top by 0.147s.

Ricciardo goes third (45.225) as Hamilton begins his first flyer on the softs.

Hamilton can only manage a PB in S1, while teammate Bottas goes quickest in S2. Another PB in S2 for the world champion as Bottas posts 44.493. Moments later, Hamilton posts 44.562, 0.069s off his teammate's pace.

A 44.868 sees Stroll go third, but the youngster is demoted when Perez bangs in a 44.629.

Vettel improves to 12th (46.179) but remains 1.686s off the pace.

Following the slowest of out laps, Verstappen begins his first flying lap. It's a weak opening sector for the Dutchman who then goes quickest in S2. At the line it's 44.574 which puts the Red Bull star third, just 0.81s off the pace. But for that weak opening sector he would have been quickest, possibly by as much as 0.4s.

Leclerc can only manage 45.759, which puts him 12th, just ahead of his Ferrari teammate.

"Strange locking, very strange," reports Kvyat.

Other than the works Ferraris, the Italian outfit's customer cars are currently filling the bottom four places.

Indeed, other than the issues at Haas, Giovinazzi has only completed 2 laps.

On the other hand, Raikkonen posts 45.704, to go 12th, ahead of the Ferraris.

In the Mercedes garage there's a change of rear wing for Hamilton.

With 12 minutes remaining, Norris (20) has completed the most laps, ahead of Kvyat (18), Sainz (17) and Leclerc (16).

As Verstappen has his latest time delated for exceeding the track limits at T9, Bottas locks up and makes a mess of the final chicane, flat-spotting his fronts in the process.

As the clock counts down, all bar the Haas pair and Giovinazzi are on track.

After being told that he did a good job of looking after his front tyres following his off, Bottas is now told he has a puncture. "That's the second puncture in a week," the Finn responds, "I had a puncture on my road car also."

As the session comes to an end, it's good to see that the top four are covered by just 0.136s.

Bottas is quickest, ahead of Hamilton, Verstappen, Perez, Stroll, Albon, Ocon, Sainz, Ricciardo and Norris.

Kvyat is eleventh, ahead of Gasly, Raikkonen, Leclerc, Vettel, Latifi and Russell.

Check out our Friday gallery from Spa, here.