Ahead of today's sole practice session the air temperature is 32 degrees C, while the track temperature is 37 degrees.

Updates for this weekend see Mercedes with a new Floor Body and Floor Edge, the German team's last significant upgrade of the season, Alfa Romeo with a new Floor Edge and Aston Martin with a new Floor Edge, Diffuser, Coke/Engine Cover and Beam Wing.

Haas's much anticipated upgrade includes a new Front Corner, Floor, Floor Edge, Sidepod Inlet, Coke/Engine Cover and Cooling Louvres, while AlphaTauri has a new Floor, Floor Fences, Floor Edge, Coke/Engine Cover, Rear Corner and Chassis.

None of the other teams have brought any upgrades though, as is rapidly becoming the norm, a number have revised liveries for this event.

The lights go green and Russell is the first out, followed by Hulkenberg, Magnussen, Verstappen and Sainz.

As more drivers head out it's mostly hards though a few are on mediums.

In no time at all there are 17 drivers on track, Norris and the Williams pair being the 'no shows'.

Russell (hard) crosses the line at 40.853 to post the first time of the weekend. Hulkenberg (medium) responds with a 39.863 and Verstappen (hard) a 39.736.

Bottas goes third, ahead of Perez, Ricciardo and Magnussen, as Norris and the Williams pair finally head out.

Sainz (hard) goes fourth with a 40.160 ahead of Piastri, as Russell raises the bar with a 39.146.

Verstappen retakes the top spot with a 37.687. Bottas goes second and Norris third.

A 38.603 sees Hamilton (hard) go second, as Alonso (hard) goes seventh.

"Woah, Lando there, he didn't see me, we nearly crashed," says Sainz. Meanwhile, teammate Leclerc (hard) goes ninth with a 39.235.

Another improvement from Verstappen (37.498) who now has a 0.602s advantage over Magnussen as Zhou goes third (38.368).

Hamilton retakes second with a 37.542, Verstappen runs wide in Turn 12.

Gasly complains he's lacking grip in the low speed corners - of which there are many here.

"We need to box, we have an issue front-left corner," Stroll is told, the Canadian clearly experiencing a serious brake issue.

Tsunoda goes third with a 38.000 on the mediums and just moments later Hamilton goes quickest with a 37.394.

Sainz complains about the bumps as the cameras pick up on his teammate taking a real pounding.

Quickest in S3, Norris goes third overall with a 37.605.

As the Aston Martin crew work on Stroll's front left brake, it appears that Alonso's has also been checked.

With around 35 minutes remaining there are just five drivers on track, among them Verstappen.

As Russell is told to "lift and coast", the Briton responds that he will drive as he sees fit.

Piastri has a big, big moments after running wide and over the kerb at Turn 8.

Stroll is out of his car as Aston Martin reports that his car has a terminal brake issue.

On mediums, Norris goes quickest with a 37.256, 0.138s up on Hamilton.

After his team made some changes to his car Ricciardo has a 'moment'. "That was quite bad," he reports as his team tell him to pit.

A number of drivers are now complaining about the bumps.

With 15 minutes remaining, the Williams pair - currently 13th (Sargeant) and 14th - make the switch to softs. The first to do so.

Sargeant improves to fourth with a 37.642, while Albon goes quickest with a 36.535.

Bottas is the next to make the switch to the red-banded rubber, followed by teammate Zhou and Verstappen as attention turn to qualifying which follows.

Norris is told to "experiment" with his lines through Turn 13 to 16.

Quickest in the first two sectors, Verstappen crosses the line at 35.912 to go top.

Tsunoda (softs) goes third ahead of his AlphaTauri teammate.

Unsurprisingly, the times are tumbling as Sargeant goes third only to be leapfrogged by Hulkenberg.

Magnussen goes second with a 36.472.

As is often the case, the McLaren and Aston Martin drivers opt not to run the softs.

A 36.474 sees Russell go third, as Verstappen complains that his seat is getting pretty hot.

Leclerc goes second (36.068) and Perez third, as Hamilton goes quickest in the opening two sectors. The Mercedes driver crosses the line at 36.193 to go third, 0.281s down on Verstappen.

"We're hitting the traffic quite hard," warns Hulkenberg as Replay shows that Hamilton lost timer in the final corner after encountering turbulence from a car running just ahead.

Onboard with Russell shows the Briton really struggling with what is a very twitchy Mercedes.

The session ends. Verstappen is quickest, ahead of Leclerc, Hamilton, Perez, Magnussen, Russell, Albon, Sainz, Hulkenberg and Gasly.

Sargeant is eleventh, ahead of Ocon, Tsunoda, Ricciardo, Norris, Zhou, Bottas, Alonso, Piastri and Stroll.

Early days, but Mercedes and Haas appear to be benefitting from their upgrades, while McLaren is struggling... and then there's Lance Stroll's continuing bad luck.

Check out our Friday gallery from COTA here.