Verstappen leads Alonso on first day of F1 testing in Bahrain

The Dutchman was top of the morning timesheets at Sakhir, although teams were focused on aerodynamic testing with prominent rakes attached to the cars in their first proper running.

Verstappen won 15 of 22 grands prix last year and will be chasing his third straight title when the 23-race season starts on March 5th.

Ferrari's Carlos Sainz was second, 0.294 slower but on top for a majority of the session, with Williams Alexander Albon third and doing the most laps (74).

Double world champion Alonso was soon up to speed for his new team, 0.029 slower than Verstappen who clocked a best of one minute 32.837 seconds and did 157 laps as the only driver to be testing all day.

"It's always like the first day back at school where everyone is in the new uniforms and seeing the cars in their colours," said Red Bull boss Christian Horner of the first day with all the 2023 cars on track together.

"It's been a sensible first session for us, I think focused on learning a little bit about RB19 which is obviously very much an evolution from the 18. A sensible morning, plenty of mileage and some good feedback."

Horner said Verstappen had worked through his programme, making setup changes in a "relatively straightforward" session, and had commented on a big bump at the end of the straight affecting all the drivers.

Mercedes and Ferrari also sounded positive, with Mercedes boss Toto Wolff noting a buzz of excitement in the garages.

The Austrian said it had been a productive day and very different from 2022 when the team were wrestling with a bouncing, 'porpoising' car.

The former champions had George Russell in action for the opening stint, with the Briton queuing up in the pitlane to be first out, before seven times world champion Lewis Hamilton hit the track later on.

"He was generally happy with the car. It seems to be balanced in the right way. There's no bouncing, which is good news, apart from that big bump," said Wolff of Russell's reaction.

"We were gathering a lot of data because that was important to correlate after last year and trying different things.

"I think we have a solid base now to work from and try to optimise the car."

Hamilton was sixth fastest and put in a hefty 83 laps.

New Ferrari team boss Fred Vasseur said his drivers were also happy.

"The first feeling was good. The most important was to do mileage and we had no issue. We were able to do the run plan and everything is going well so far."

Sainz was third fastest on the combined day 1 timings, with teammate Charles Leclerc fourth and McLaren's Lando Norris fifth despite losing some track time for repairs to his car.

The red flags were waved after nine minutes when Brazilian Felipe Drugovich, standing in for injured Canadian Lance Stroll, stopped his Aston Martin on track with an electrical problem.

German driver Nico Hulkenberg started his comeback at Haas, and was sixth of the 10 drivers in action, while Australian rookie Oscar Piastri did 52 laps for McLaren but propped up the timesheets.