Lando Norris ends opening day quickest in the McLaren
George Russell for Mercedes second, Red Bull's Max Verstappen third
Lengthy delay during afternoon session due to circuit-wide power cut
First look at Lewis Hamilton for Ferrari
Day two starts at 07:00 GMT on Thursday
Season-opening Australian Grand Prix 14-16 March
Verstappen aiming for fifth consecutive drivers' title in 2025
McLaren begin defence of constructors' championship
Get involved: #BBCF1
The word 'sandbagging' is thrown about a lot in testing, but what does it mean?
In Formula 1, sandbagging is when a team or diver intentionally completes slower lap times to hide their car's true potential.
Fernando Alonso is back in the Aston Martin garage, his engineers have bolted on a new set of tyres and have a look at the car.
The back of Alex Albon's Williams has been painted in red flow-vis paint so his team can check the air flow at the rear of his car.
Image source, Getty Images
Chris Medland
F1 journalist in Bahrain
Image source, Getty ImagesThe weather in Bahrain when F1 visits is usually warm and sunny, with some pretty windy days the biggest challenge that teams tend to face. This week, however, it's unseasonably cold.
When the sun breaks through, it's still comfortably warmer than the UK, but the high temperature today is just 16C, and a strong wind is lowering how that feels. Given running is taking place until 7pm each day, it feels particularly cold at night.
Why is that important? Because the majority of races take place in hot conditions during the season, so teams design cars - and Pirelli creates tyres - to operate in those temperatures.
This week, they might not get such an accurate read on how both their cars and the tyres perform, particularly when it comes to car cooling.
Fernando Alonso has topped the leaderboard. He's on a lap time of 1:31.874 on the medium tyres.
18-year-old Andrea Kimi Antonelli makes a quick pitstop before re-joining the track.
Image source, Getty Images1. Liam Lawson (Red Bull) - 1:32.036
2. Yuki Tsunoda (Racing Bulls) +0.247
3. Alex Albon (Williams) +0.396
4. Nico Hulkenberg (Sauber) +0.475
5. Lewis Hamilton (Ferrari) +0.651
6. Fernando Alonso (Aston Martin) +1.117
7. Jack Doohan (Alpine) +1.282
8. Andrea Kimi Antonelli (Mercedes) +1.993
9. Oscar Piastri (McLaren) +2.313
10. Oliver Bearman (Haas) +3.705
Oooh, There's a little bit of action as Alex Albon tries to overtake the Sauber of Nico Hulkenberg.
Albon is now up in the third spot.
Image source, Getty ImagesThe Sakhir circuit joined the F1 calendar in 2004, and has been used for pre-season testing since 2021.
The track is considered a good choice for testing primarily because of its balanced layout. Sakhir features a mix of high, medium and slow-speed corners, as well as a couple of long straights, meaning top speed, acceleration, cornering, and tyre usage are able to be analysed relatively equally.
Bahrain also has very little rainfall, meaning teams are almost guaranteed consistent weather and dry running. The Bahrain Grand Prix has never once been impacted by rain since it joined F1.
Hello Oscar Piastri. The McLaren is out of the garage now. The papaya team are running a different programme from the rest of the pack.
Image source, Getty ImagesOliver Bearman is making his way down the track in Bahrain.
I love the bear design on his helmet, very creative.
He's currently in ninth, but can he go faster?
Image source, Getty ImagesThere's been a few shake ups across the grid for the 2025 line-up.
McLaren and Aston Martin are the only two teams who have stuck with their drivers.
McLaren duo Lando Norris and Oscar Piastri and Aston Martin's Fernando Alonso and Lance Stroll.
The skies are still cloudy in Bahrain as Lewis Hamilton takes a quick trip to the pit lane.
He's back out on track and whizzing down the Sakhir track.
Hamilton is still topping the leaderboard, with Alex Albon and Fernando Alonso behind him.
Image source, Getty ImagesLiam Lawson, four-time world champion Max Verstappen's new rookie team-mate, is out in the Red Bull first, while 43-year-old Fernando Alonso is taking the opening session on day one for Aston Martin.
Image source, Getty Images
Image source, Getty ImagesLewis Hamilton is back out on the track in Bahrain.
He's set a lap time of 1:32.621 and jumped up to the top spot.
Image source, Getty ImagesSpeaking of Alex Albon, he's just set a lap time to top the leaderboard.
He's set a time of 1:32.862 on the medium tyres.
The green Sauber of Nico Hulkenberg is back in the garage as we follow Racing Bull's Yuki Tsunoda, who is currently third.
It's been a little quiet in the McLaren and Williams garages, Oscar Piastri and Alex Albon are yet to set lap times, but we still have three hours to go.
Lewis Hamilton's trainer, Angela Cullen has returned to work with the seven-time world champion.
They've worked together from 2016 to early 2023.
Image source, Getty ImagesAston Martin's Fernando Alonso is up in second now, with a lap time of 1:33.359.
At the age of 43, he is the oldest driver on the grid.
2024 F2 champion Gabriel Bortoleto is his protege, I'm sure he'll have lots to learn from the two-time world champion.
Image source, Getty Images1. Jack Doohan (Alpine) - 1:33.196
2. Nico Hulkenberg (Sauber) +0.646
3. Yuki Tsunoda (Racing Bulls) +1.221
4. Lewis Hamilton (Ferrari) +1.890
5. Liam Lawson (Red Bull) +2.232
Ian Fergusson
BBC weather forecaster
The three-day test will be held in unseasonably cool conditions; max temperatures ~16-19C.
A brisk northwesterly wind will feature, with blowing dust likely on circuit.
Some light showers are possible Thursday afternoon.
Image source, Getty ImagesJack Doohan is still topping the leaderboard, he has some bright green flow-vis paint on the right side of his car.
The TV camera has panned on to Charles Leclerc in the Ferrari garage and - is he taking a nap?
Nope, he's just opened his eyes and smiled.