Ahead of today's opening session, the air temperature is 28 degrees C, while the track temperature is 46 degrees. It is bright, sunny, beautiful day.

In terms of upgrades, Red Bull has a new Sidepod Inlet, Coke/Engine Cover, Floor Body, Beam Wing and Rear Wing, while Ferrari, which has brought its upgrade programme forward following the nightmare of Montreal, has a new Rear Wing, Coke/Engine Cover, Floor Fences, Floor Body, Floor Edge, Diffuser and Halo.

Aston Martin has a new Front Suspension, Front Corner and Rear Corner, while RB, like its fellow Italian team has a whole raft of upgrades including a new Front Corner, Coke/Engine Cover, Sidepod Inlet, Floor Body, Rear Wing and Beam Wing.

Stake has a new Rear Wing and Front Corner, while Haas has a new Rear Impact Structure. Mercedes, McLaren, Alpine and Williams don't have any upgrades.

Having been put under intense pressure since Miami, this track should suit Red Bull more, though looking at those upgrades Ferrari is far from throwing in the towel.

Only one reserve driver in action this morning, and that is Oliver Bearman who replaces Nico Hulkenberg at Haas.

The lights go green and Bottas leads the way, followed by Alonso, Magnussen, Russell and Norris.

This being a test track of long-standing, the aero rakes and flo-vis is in abundance.

As more cars emerge it's a mixture of hards and mediums, though most have opted for the white-banded rubber.

In no time at all there are 18 drivers on track, Verstappen and Albon the only two yet to appear.

Magnussen posts the first time of the weekend (18.513), but Russell subsequently crosses the line at 17.024.

Courtesy of that impressive upgrade package, Tsunoda posts a 16.917, while Sainz goes third, ahead of Perez, Hamilton, Ocon and Stroll.

Six minutes in and Verstappen finally heads out, leaving Albon as the only no-show.

Russell retakes the top spot with a 15.868, as Verstappen gores second with a 16.254.

Albon finally heads out.

Ocon goes third with a 16.788, as Albon posts a 17.432 to go eighth.

Leclerc improves to third and Hamilton fourth.

"No power, no power," reports Sainz, who, having made a few adjustments, subsequently improves to second with a 15.899.

However, the Spaniard is demoted when Verstappen improves to 15.424.

The leading ten drivers are all on hards, while Albon (11th) is the highest placed medium runner.

Suffering understeer, Perez queries whether there is a throttle issue. He is told to pit in order that the issue can be discussed... in private.

"The car is horrendous for now," complains Leclerc.

Norris goes fourth with a 15.967, despite complaining of instability in the fast corners, a situation not helped by a stiff wind that is buffeting the track. Teammate, Piastri goes seventh (16.234) as he too complains that his car is "nervous at the rear".

After 25 minutes, the only driver yet to post a time is Alonso, however the Spanish Samurai is on track. Teammate Stroll is currently 13th on 17.106.

Alonso posts an exploratory 17.423 to go 17th.

Bearman, who some believe could replace Sargeant at Williams in the coming weeks, is currently 20th with a best time of 17.725.

Russell goes second with a 14.753, Sainz having previously posted a 14.572.

Perez (softs) goes second (14.692) but is demoted when his teammate, also on the red-banded rubber, crosses the line at 14.252.

As more drivers switch to softs, Ricciardo goes seventh and Norris eighth, both on the red-banded rubber.

Tsunoda has a scary moment as he comes across a slow Mercedes (Russell), the Japanese unable to see which side of the track the Briton is going for as he seeks to get off the racing line.

Albon improves to sixth on the mediums, as teammate Sargeant claims tenth.

Quickest in the opening sector, Norris bangs in a 14.228 to leapfrog Verstappen by 0.024s.

Magnussen goes tenth and Bearman 13th.

The session is red-flagged after debris is seen to fall from Alonso's Aston Martin.

"Exit, Turn 9, something fly from the front wing, so better check," warns the Spaniard as the offending debris is removed from the track.

The session is stopped just as a number of drivers were beginning their race sims, however it resumes after a couple of minutes.

Piastri is first out, followed by Bearman, Norris, Ocon and Verstappen.

Bottas (softs) improves to eleventh with a 15.472, as Alonso goes ninth (15.222) also on the red-banded rubber.

Stroll goes 14th with a 15.512.

"Who is the Aston Martin?" asks Leclerc of a dawdling Stroll.

Other than traffic, tyre deg is also clearly an issue, though both have always been the case here.

As he pits, Leclerc complains that there was something wrong with his clutch as he pitted.

An early pace-setter, Tsunoda has only completed 13 timed laps and is currently in the pits.

At Mercedes, Russell is on the hards while his teammate is on mediums, the German team opting for a split strategy, McLaren having adopted a similar tactic.

"I think there is something wrong with the car," reports Gasly, "I can't... it's undriveable."

"The clutch keeps anti-stalling," reports Verstappen.

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

Leclerc is eleventh, ahead of Bottas, Gasly, Stroll, Ricciardo, Zhou, Magnussen, Sargeant, Bearman and Tsunoda.

First blood to McLaren, certainly in terms of Norris, though Piastri was probably compromised by the red flag.

Verstappen is only 0.024s off the pace, with teammate Perez just 0.4s behind.

Home hero Sainz is the quicker of the two Ferraris, his teammate clearly unhappy with his car, while Russell has the edge on Hamilton.

Early days, but not what we expected from RB with that major upgrade package, a situation not helped by Tsunoda's lack of running.

An interesting opening session.

Check out our Friday gallery from Barcelona here.