Fernando Alonso has ended the first day of in-season testing at Silverstone atop the timesheets as rainy conditions prevented any driver from improving their morning benchmarks.
The two-time world champion – one of only four full-time race drivers staying on at Silverstone following the British Grand Prix – hit the front with a super-soft shod lap of 1min 31.290secs in the morning, putting him almost 1.6s clear of the opposition.
However, the onset of rain during the lunch break would curtail any chance of improvements being made during an extended afternoon session, even if the McLaren-Honda driver didn't waste the opportunity for track time by notching up a total of 105 trouble-free laps.
With the final order mirroring that of the morning, Esteban Ocon remained second on the timesheets, completing the most running at 123 laps, ahead of Williams' Alex Lynn.
Charles Leclerc was fourth for Ferrari but limited his afternoon action to just two separate installation laps, the Monegasque completing just 19 laps all day in the end.
Debutant Nikita Mazepin was fifth in the Force India, but limited to a relatively meagre 35 laps, ahead of Carlos Sainz – whose day finished an hour before the end of the session – and Haas newcomer Santino Ferrucci.
With no treaded versions of the 2017 prototype Pirelli tyres being trialled on the Mercedes W05, Pascal Wehrlein didn't make it back on track to end his day eighth, ahead of Rio Haryanto and Sergey Sirotkin. Having managed just seven laps in the morning, Pierre Gasly got back out to complete 51 laps in total, but with no chance to improve a best time that was 12secs off the pace.
The afternoon session was briefly stopped after a piece of wood fell from the lighting gantry on the start-finish straight, albeit without consequence.