Championship leader Oscar Piastri goes fastest of all on the hard compound, clocking 1:44.979, six tenths quicker than Max Verstappen.

Williams don't seem quite sure what the issue is with Carlos Sainz's car. It is in the garage with several people crowded over the back of it seemingly trying to work out what's wrong.

Charles Leclerc goes second quickest in the Ferrari, half a second off Max Verstappen's time.

And Max Verstappen kicks off his session on the mediums with 1:45.545 on the mediums, sending him top of the pile.

Lando Norris sets the early pace with a 1:46.082 on the hard tyres.

Just seen the replay and Carlos Sainz's issue started almost as soon as he got out of the pits.

He's back at base now and the team will look into that one.

Meanwhile, Max Verstappen - who is on mediums - is on a fast lap.

Problems are the early theme here as Lance Stroll is told to box with an issue as well.

Problems for Williams already as Carlos Sainz reports he cannot accelerate and he will "have to limp home". He has pretty much the whole circuit to limp along.

Andrew Benson
BBC F1 correspondent at Spa-Francorchamps

Image source, Getty Images

Ferrari are introducing a long-anticipated modification to their rear suspension this weekend. This is believed to be addressing an issue the team have been having in not being able to run the car as low as they want for optimum performance without damaging the floor too much and risking disqualification, as both cars were in China.

The team says: "This revision of the rear suspension geometry triggered a re-optimisation of wishbone fairings as well as lower and upper winglet cascades, with the aim of maximising aerodynamic efficiency.” The change is also aimed at improving drivability and feel.

Other teams with significant upgrades this weekend are Red Bull, Aston Martin and Williams.

Red Bull have a new front wing and revised front suspension and aerodynamics around the sidepod inlet and engine cover. Aston Martin have new front and rear wings and nose, and Williams a new floor and bodywork.

Off we go with one hour of practice.

Plenty keen to get out there straightaway, understandably given it is the only practice session of the weekend.

Hard is the favoured compound.

Following Christian Horner's removal as Red Bull team principal and chief executive, Laurent Mekies takes charge for the first time after his promotion from second team Racing Bulls.

The 48-year-old Frenchman had been at Racing Bulls since the start of the 2024 season and was previously racing director for Ferrari.

It is the first time anyone other than Horner has been in charge of Red Bull's main F1 team since their debut in 2005.

Englishman Alan Permane, 58, has been promoted to team principal of Racing Bulls from his position as racing director.

BBC Sport's Harry Benjamin picks his five things to look out for at the Belgian Grand Prix at Spa Francorchamps this weekend, with help from BBC Radio 1 DJs Melvin Odoom and Jeremiah Asiamah.

Ian Fergusson
BBC weather forecaster

[As of 15 mins before practice] Air temp 20.1C & track 34.7C. Light wind from the NW; dry, with FIA official risk of rain 10%. A similar low risk rest of Fri & Sat (fog likely on Sat AM). Current FIA guidance is for a 60% shower chance during Sunday's race.

There's just the one practice session this weekend because the Belgian Grand Prix features a sprint race.

Here's today's key timings (all BST):

Practice session: 11:30-12:30 (BBC Radio 5 Sports Extra 2, BBC Sounds and smart speakers)

Sprint qualifying: 15:30-16:14 (BBC Radio 5 Sports Extra 2, BBC Sounds and smart speakers)

Andrew Benson
BBC F1 correspondent at Spa-Francorchamps

Image source, Getty Images

Lando Norris says he feels “more of a threat” to McLaren team-mate Oscar Piastri after progress made in his understanding and feel for the car in recent races.

Norris comes to the Belgian Grand Prix on the back of consecutive victories in Austria and Britain, albeit he inherited the Silverstone win after Piastri was penalised for driving ing dangerously behind the safety car.

“Do I feel more of a threat now? Yes,” Norris said. “But am I happy enough still with where I'm at, where the car is and my harmony with the car? It's still not to the level that I want.”

A new part in the front suspension of the McLaren - which was introduced to help Norris feel the front tyres more, but which Piastri does not feel he needs and is not using - has helped Norris, but he has also worked on his driving with the team behind the scenes. Yet he says he still does not feel quite back to the the level he was at last year, when he was consistently the fastest McLaren driver.

“I certainly feel happier. Austria was a place I felt the happiest, even happier than I was in Silverstone. With the car, with the knowledge of where I can push, how I can push and all those things.

“We're still trying to work on things to give me more from the car in order to allow me to unlock that more often, like I was doing last season,” said Norris.

“The most positive thing from those two weekends was just that the pace was better from the off and I was more comfortable with the car and in understanding how to get the most pace from it. At times that brings more of a smile to my face than just winning the race itself. Because it's progress, it's seen progress and that's always a very good thing, it's a very rewarding thing.”

Things are heating up in the title race as we move into the second half of the seaosn.

After winning the past two grands prix, Lando Norris has narrowed the gap in the drivers' championship to his McLaren team-mate Oscar Piastri to eight points.

Will Norris complete a hat-trick of race wins at the Belgium Grand Prix this weekend?