Fernando Alonso topped the timesheets for F1's young driver test in Abu Dhabi, the Renault driver heading the Mercedes pair of Nyck de Vries and Stoffel Vandoorne.
The single day test allowed Alonso to spend an entire day - or 104 laps - at the wheel of Renault's 2020-spec car and continue his preparations for his return to the grid next season.
The Spaniard lost no time getting down to business, but a qualifying simulation run in the latter part of the day yielded a 1m36.333s that was 0.026s faster than Esteban Ocon's best effort in qualifying for the Abu Dhabi GP last weekend.
The day's runner-up Nyck de Vries, who clocked in 0.262s behind Alonso, earned himself bragging rights for outpacing Vandoorne, his Mercedes Formula E teammate. It was also the Dutchman's very first F1 test.
Alfa Romeo's Robert Kubica was fourth fastest, 1.113. adrift from Alonso, in a session that may have been the Pole's final outing in F1.
AlphaTauri's rumored-to-be 2021 driver Yiuki Tsunoda ended the session a creditable fifth.
Sixth-placed Juri Vips was Red Bull's fastest runner on-board the team's RB16, with teammate and F1 veteran Sebastien Buemi ending his day P12.
Over at Ferrari, Antonio Fuoco was P7, a few tenths faster than fellow Scuderia member Robert Shwartzman who was P11 but who put the most laps on the board.
The Italian edged Alfa's second driver Callum Ilott, while Renault junior Guanyou Zhou and Williams' Jack Aiken rounded off the top ten.
Marino Sato was 13th quickest just ahead of Roy Nissany, while Mick Schumacher ended his day with Haas last but with 125 laps under his belt.