Ahead of today's sole practice session the air temperature is 29.8 degrees C, while the track temperature is 50.4 degrees.

Ferrari set the pace yesterday, with Charles Leclerc quickest in the morning, and teammate Carlos Sainz setting the pace in the afternoon.

However, the Spaniard is already facing a 10-place grid drop for taking on a new control electronics and with Ferrari tipped to take on a whole new power unit that may well increase.

Max Verstappen was unhappy with his car's balance, the Dutchman suffering a lot of understeer, while Sergio Perez said he simply wasn't "comfortable" with the car.

Though the Mercedes pair were fourth and fifth, Lewis Hamilton claims the German team is further off the pace than anticipated, though, like most of the utterings from the German team, this should probably be taken with a pinch of salt.

McLaren and AlphaTauri have brought the biggest package of upgrades and both teams claim that they are paying off, while Kevin Magnussen and Fernando Alonso both looked good.

Tyre deg looks likely to be the big talking point this weekend, and it is going to be interesting to see the pace once the drivers try the hards. The softs will only be used for qualifying, and yesterday we witnessed several drivers managing to get a second hot lap out of the red-banded tyres.

The lights go green and Perez is straight out of the box, subsequently followed by Magnussen, Stroll and Vettel. The Mexican is on mediums, the Dane softs and the Astons on hards.

The Mercedes drivers are running different rear wings, certainly in terms of the lower element.

Perez posts the first time of the day, a 22.628, as Verstappen, Russell and Ocon head out. Magnussen posts a 34.768.

Verstappen wastes no time in getting down to business, the world champion posting a 32.837.

As Perez improves to 33.305, he is told that his biggest loss to his teammate is mid-corner speed in Turn 4.

Hamilton heads out on softs, the Briton subsequently going fourth with a 34.592.

Magnussen runs wide in Turn 11.

Hamilton is told he is 1.7s off Verstappen's pace on mediums. "We're losing out on straight-line speed mainly," the Briton is told. With the seven-time champion having opted for that big development rear wing he is likely to reconsider the move.

As Verstappen improves to 32.808, Ocon goes third and Alonso fifth.

Despite the updates, Gasly can only manage 9th, 2.3s off the pace. The Frenchman is subsequently demoted by his teammate who is only 2.2s off the pace.

A 33.999 sees Bottas go third, ahead of Alonso, Russell, Ocon and Hamilton.

After 17 minutes, only 14 drivers have posted times, while Latifi and Schumacher have yet to appear.

Sainz goes second with a 33.217 as Leclerc goes seventh with an exploratory 34.233.

At which point the FIA confirms that both Sainz and Magnussen have taken on new power units and will therefore start from the back of the grid.

Stroll complains of a lot of air in his visor.

Russell aborts his first flyer on softs after making a mistake in the opening sector.

In quick succession, Leclerc spins at Turn 12, while Perez runs wide at Turn 11 and Norris at Turn 3. Sainz gets in on the act by running wide in Turn 11.

The timing screen shows Zhou as running full wets.

Gasly improves to fourth with a 33.869, albeit 1.061s off the pace.

"Bro! F****** traffic! Bro, that was so dangerous," says Tsunoda.

Clearly on a high fuel run, Ricciardo is the driver for one of F1's infamous 'Sound FX' laps, the Australian posting a 35.143 but remaining 20th.

On successive laps, Perez goes wide at Turn 3.

A 33.255 sees Hamilton improve to third on the softs.

Sainz and Leclerc both begin their qualifying sims, while the Spaniard remains second (33.172) he is subsequently demoted when his teammate stops the clock at 32.909.

However, Verstappen remains quickest with a time posted on mediums.

Albon improves to sixth (33.558) and Latifi seventh (33.841) suggesting that this session is far from over.

Norris splits the Williams pair with a 33.669, but is demoted when Russell goes sixth with a 33.376.

With 14 minutes remaining, Verstappen is one of several drivers yet to try the softs in this session, the others being his teammate, the Aston Martins and Alpines.

Ricciardo improves to tenth with a 33.788.

Sainz goes quickest in S1, but appears to back off in S2, as does his teammate. That said, the Spaniard posts purple in S3, crossing the line at 32.626 to go top, 0.182s quicker than Verstappen.

At which point the Dutchman finally heads out on softs. As the world champion goes quickest in the first two sectors, Leclerc complains that he is unable to improve on his second lap. Verstappen crosses the line at 32.272.

However, teammate Perez aborts his lap and remains 5th.

"Feels terrible," complains Stroll who is unable to improve on 19th (34.235). Teammate Vettel, who is currently 20th, is still in his garage with mechanics working on the car. Aston Martin will only confirm that it is "car damage".

"I have no grip guys," complains Ocon, "no grip." The Frenchman is currently 17th, while teammate Alonso is 7th.

A late mix-up almost sees Verstappen trip up over Schumacher.

The session ends. Verstappen is quickest, ahead of Sainz, Leclerc, Hamilton, Perez, Russell, Alonso, Albon, Norris and Tsunoda.

Ricciardo is eleventh, ahead of Latifi, Gasly, Bottas, Zhou, Magnussen, Ocon, Stroll, Schumacher and Vettel.

Check out our Saturday gallery from Le Castellet here.