Triple world champion Max Verstappen made sure it was business as usual, despite uncertainty surrounding his Red Bull team boss Christian Horner, by leading the way as Formula One began pre-season testing in Bahrain on Wednesday.

The 26-year-old Dutch driver, winner of a record 19 of 22 races last season, was top of the morning session with a lap quicker than the fastest effort on the first day at the same Sakhir circuit last year.

His time of one minute and 32.548 seconds in the morning sunshine compared to 1:32.837 last year. Ferrari's Charles Leclerc was second with Fernando Alonso third for Aston Martin and the last driver within a second of Verstappen.

Australian Oscar Piastri lapped fourth fastest for McLaren. The season starts in Bahrain on March 2. Although testing times do not amount to much, with teams working through their own programmes with different priorities, the Red Bull RB20 looked an impressive and aggressive evolution of the car that won all but one race last year.

Verstappen looked composed and smooth at the wheel as he completed 65 laps -- more than a race distance at the desert circuit. Horner, who has denied allegations of inappropriate behaviour levelled against him by a female employee, was attending testing and said at last week's launch that he was working as normal.

Williams driver Alex Albon was the only driver to experience a notable problem, stopping his car on track with 21 minutes remaining of the first session. Mercedes had George Russell in the car, whose front wing gained plenty of attention, and the Briton lapped sixth quickest.

Team boss Toto Wolff said the mood in the team was positive, with Mercedes putting the emphasis on creating a stable platform for development and spending time making changes to the car in the garage. "We had a filming day yesterday and then some aero running this morning with no relevant lap times," added the Austrian.

"So far the feedback from the drivers was yes, this is something we can start to work with and that is encouraging."

Teams have just three days of testing before the season starts next week.