Mercedes' George Russell ended the final morning of pre-season testing in Barcelona as fastest man, as both of 2021's title rival teams responded to the pace shown by McLaren and Ferrari over the first two days.
While Red Bull's Max Verstappen led the field halfway through the morning, having set a 1:19.765 on the Medium (C3) tyres, Russell stormed to the top of the times with just over 90 minutes remaining in the session.
The British driver set a 1:19.608 on the Soft (C5) compound, pipping Charles Leclerc's fastest time from Thursday as the Ferrari driver clocked a 1:19.689 on day two (with C3 Mediums).
But Russell didn't stop there, as he fitted another set of Softs in the run-up to the lunch break. He duly proceeded to put in a 1:19.233, easily the fastest time of the day and of the test overall. With the track set to be artificially dampened to enforce Intermediate and Wet tyre running in the afternoon, it's highly unlikely Russell's time will be beaten.
Behind the Mercedes, Verstappen finished in second place. After Red Bull's truncated day on Thursday due to a gearbox issue, the Dutchman logged 55 laps during the morning with a quickest time of 1:19.756 set on the Medium (C3) tyre. This was enough to keep him a tenth clear of Aston Martin's Sebastian Vettel, who put in a 1:19.824 on the Soft (C4) tyre just before the lunch break.
This time from Vettel pipped Leclerc's best by just 0.007s, with the Monegasque settling for fourth at the chequered flag after completing 44 laps.
Nicholas Latifi only completed five laps during the morning, but ended up in fifth, as Williams opted to run both of their drivers during the final hours of dry running. Wednesday pace-setter Lando Norris was sixth for McLaren, racking up 52 laps of the Circuit de Barcelona-Catalunya.
Numerous red flags interrupt the flow
With the teams seemingly cranking up the pace a little on the final morning, there were numerous red flag interruptions that disrupted the session.
Alpine's Fernando Alonso brought out the first red flag as he came to a very smoky halt on track less than one hour into the morning. While the car was recovered to the pits, the team have since confirmed that a hydraulic issue was the cause of his stoppage. The car will not be going on track again on Friday, meaning their Barcelona test has concluded prematurely.
Pierre Gasly then became the first driver to crash during testing, as he lost control of his AlphaTauri and went off into the barriers. With Gasly unhurt, the session was stopped while the car was retrieved.
Shortly after that, Alfa Romeo's Guanyu Zhou brought out the red flags once again as he spun at the beginning of the final hour. The car was brought back to the pits and, shortly after the session resumed, Zhou was back on the circuit. However, it appeared all was not well with the C42, as Zhou almost immediately broke down – triggering the fourth red flag of the morning.
Less than 10 minutes before the end of the morning, Vettel was next to cause a stoppage – the Aston Martin driver encountering an apparent technical issue on his AMR22 in the final sector of the lap. Given the proximity to the lunch hour, the session was not resumed.
Elsewhere, there were also issues for Haas and Nikita Mazepin. With the team running a plain white livery after pulling the Uralkali branding from their car and their trucks, Mazepin had only completed nine laps of the circuit when he encountered a suspected leak. He withdrew to the garage, and Haas are yet to send the car back out on track.
You can stay up to date with all the action from Barcelona in the dedicated RacingNews365.com live blog.
With F1 pre-season testing getting underway in Barcelona this week, our journalists Dieter Rencken, Mike Seymour and Thomas Maher look ahead to what to expect.