Ferrari star Lewis Hamilton set the fastest lap time of testing so far during Thursday's pre-season testing morning session at the Bahrain International Circuit.
The seven-time world champion suffered a disappointing first day of testing on Wednesday, only setting the 13th fastest time, one second behind team-mate Charles Leclerc, but bounced back with a stunning lap on Thursday.
While times are still not particularly important for teams at this stage, there was evidence of some faster running going on for various drivers, with George Russell sitting in second just behind his former team-mate.
The Williams of Carlos Sainz finished the session up in third, with Pierre Gasly in fourth, while the McLaren of Oscar Piastri collided with Nico Hulkenberg in a bizarre incident in the final hour of the session, causing some damage to the Australian's car.
Testing is not known for on-track collisions between drivers, and Sky F1 pundit Karun Chandhok suggested it was 'odd' that Hulkenberg was dawdling on the racing line while Piastri was completing a lap.
Meanwhile, Thursday's morning session suffered an hour-long delay for eight of the teams, who had decided not to include any intermediate or wet tyres in their allowance for Bahrain, after precipitation fell at the circuit.
Only Aston Martin and Haas brought some form of wet tyre to the test, but for nearly an hour the track was too dry for intermediate tyres, yet too wet for any useful slick running.