Fernando Alonso recorded the quickest time for McLaren-Honda during the opening day of the second in-season test at Silverstone, before rain affected the afternoon running.
Alonso worked his way down to a 1:31.290 on the Super Soft tyres in the morning, before a heavy shower over lunchtime left the circuit drenched prior to the afternoon session.
Alonso’s time proved to be 1.543s quicker than Esteban Ocon, who received his first taste of the Mercedes W07 Hybrid, having piloted Renault’s RS.16 during practice for the British Grand Prix.
Ocon completed the most mileage, having racked up 123 laps of Silverstone.
Williams development driver Alex Lynn was 3.143s behind Alonso in third place as he led a train of closely-matched drivers, ahead of Ferrari’s Charles Leclerc.
Leclerc, the current GP3 Series leader, completed only a short stint of laps during the morning session as he got to grips with the SF16-H, and appeared only briefly in the afternoon.
Russian Formula 3 racer Nikita Mazepin made his Formula 1 test bow with Force India and placed fifth, ahead of regular Toro Rosso driver Carlos Sainz Jr.
GP3 rookie Santino Ferrucci became the first American driver to sample Haas machinery and was seventh, having accumulated sufficient mileage for a superlicense, while Pascal Wehrlein notionally set the eighth best time.
Wehrlein, Manor’s race driver, was piloting Mercedes’ 2014 car, the W05 Hybrid, as part of Pirelli’s programme to gather tyre data for 2017.
Wehrlein did not run at all during the afternoon session due to the wet conditions.
Rio Haryanto was ninth best for Manor, ahead of Renault tester Sergey Sirotkin and Red Bull junior Pierre Gasly, fresh from his maiden victory in the GP2 Series.
Gasly completed an installation lap shortly after the morning session began with a halo fitted to his RB12, as development for the system’s potential 2017 introduction continues.
Sauber was once again absent as it attempts to ready its substantial upgrade package prior to the summer break.
The rain which fell across the circuit over the lunch break impacted on the afternoon schedule, with most teams completing only a handful of laps in wet conditions.
The session was briefly halted mid-afternoon when a piece of wood fell from the pit gantry onto the start/finish line, but there were no other stoppages.
The test will conclude on Wednesday, with Kimi Raikkonen and Valtteri Bottas back in action for Ferrari and Williams respectively.
Stoffel Vandoorne will return to the cockpit of the McLaren, with Jolyon Palmer in action for Renault and Manor youngster Jordan King getting his second taste of the MRT05.
Sergio Sette Camara will make his Toro Rosso debut while Ocon, Gasly, Mazepin and Ferrucci will continue for their respective teams.