Just over 20 minutes into the session and still no times put down yet from Williams, but both their drivers are on the track now.

Max Verstappen reports that "something is hanging loose" on his end plate. He's boxed so that the team can have a look at that.

It is pretty quiet on the circuit with several other drivers back in the pits to go over the early bit of data that has been gathered in the first part of this practice session.

1) Verstappen 1:06.598 (H)

2) Alonso +0.058 (M)

3) Hamilton +0.144 (H)

4) Perez +0.173 (H)

5) Bottas +0.672 (M)

6) Ocon +0.726 (M)

7) Stroll +0.767 (M)

8) Norris +0.770 (M)

9) Gasly +0.828 (M)

10) Guanyu +0.857 (M)

We're 15 minutes into the session and the times keep on getting quicker at the top of the order as Max Verstappen moves back into P1, going 0.058s quicker than Fernando Alonso.

Fernando Alonso has now risen to the top as he does a 1:06.656 on the medium rubber. Lewis Hamilton also improves and goes P2, 0.086s slower than his former team-mate.

Nothing yet from the two Williams of Alex Albon and Logan Sargeant which you would imagine is not ideal given this is the only practice session of the weekend.

The track is still lacking a bit of grip in places as Valtteri Bottas locks up at Turn One, while Yuki Tsunoda locks up.

Image source, Getty Images

Fernando Alonso has been on the podium six times this season but one of the few times he failed to finish in the top three was in Azerbaijan, which held the first Sprint race of the year.

"I think the Sprint weekend will not be ideal for us," he said.

"We still have more time maybe of free practice with our new upgraded car. We still need to understand and optimise the package a little bit and in Austria, obviously with the Sprint, we will have only FP1 to do that. But it is what it is."

Esteban Ocon and Fernando Alonso are on medium tyres and are currently fourth and fifth quickest respectively.

Changes at the top as Max Verstappen takes over from Sergio Perez with a time of 1:07.145, but Perez responds by going 0.034s quicker.

Lewis Hamilton is up to third with a time of 1:07.204. All three are on the hard tyres.

Sparks fly from behind Lewis Hamilton's Mercedes as he rumbles over one of the kerbs. Hamilton's first timed lap is 0.6 seconds down on Sergio Perez's time.

Sergio Perez, on the hard compound, sets the early pace with a 1:07.595, half a second quicker than Max Verstappen's first timed effort.

Bit of early banter between the championship leader and his engineer as Max Verstappen completes his first lap.

"Radio check," says his engineer, before adding: "receiving you loud..."

"But not clear?" chuckles Verstappen.

Lewis Hamilton is among the drivers to head straight out as practice gets under way.

Seconds before the only practice session of the weekend gets under way and no-one is going to want to waste a moment of this small window of opportunity to tune things up.

Ian Fergusson
BBC weatherman

Air temp 27C & track 44.8C. Dry; a few showers are building in wider area. FIA official risk of rain 10%.

Radio coverage across the weekend will be live on the BBC Sport website and App.

Today's practice commentary gets under way at around 12:25 BST.

Andrew Benson
BBC Sport’s chief F1 writer

This is a big weekend for McLaren. The team are introducing what principal Andrea Stella has called a “milestone” upgrade, one they hope will turn their season around after a difficult start. McLaren were open from the launch of the car that they had missed their development targets, not seen opportunities for lap time until it was too late. This race sees the debut of the design with which they would ideally have wanted to start the season.

The FIA upgrade sheets detail how extensive it is - McLaren say there is a “fully revised floor”, along with new sidepod inlets, a new fairing on the halo and a new sidepod and engine cover shape.

It is the start of a series of upgrades being introduced over the next three races and the rush to get it ready has meant only Lando Norris’ car has it. Oscar Piastri has to struggle on with the old design for this weekend. Norris said it was “exciting”. He admitted that introducing such a big chance on a sprint weekend, where there is only one practice session before the car specification is locked in is not ideal. “It is going to be tough,” Norris said, “but we still think it’s the best thing to do. I am looking forward to it.”

Image source, Getty Images

Sergio Perez missed yesterday's media day because he wasn't feeling well but Red Bull have confirmed he is in the paddock and OK to take part in today's qualifying day.

He will be desperate to reignite his title charge with a high points-scoring weekend.

Image source, Getty Images

Formula 1 introduced a new format for 'sprint' races for the 2023 season.

The 'sprint' - a shorter race held on Saturday - has been made independent of the grand prix and will have its own qualifying session, known as the 'sprint shootout'.

Qualifying to set the grid for the main grand prix is held today and there will then be a shorter qualifying session, to the same knockout format, on Saturday to set the sprint grid.

The 'sprint' qualifying will have three sessions, with the slowest five cars eliminated at the end of the first two, but the sessions will be cut to just 12, 10 and eight minutes. The three sessions in a standard qualifying run for 18, 15 and 12 minutes, respectively.

The idea behind the changes is to introduce more jeopardy into the 'sprint' by encouraging drivers to take more risks.