Fernando Alonso ended the opening day of the Silverstone test fastest for McLaren, after a day plagued by changeable weather conditions.
Most of the field completed their fastest times in the morning period, which took place in dry and favourable conditions to that of the afternoon period, where improvements were practically impossible.
The Spaniard ended the day +1.5 seconds ahead of DTM racer Esteban Ocon, who was making his debut for championship leaders Mercedes. The Frenchman completed the most running of the day, racking up 123 laps in total.
Williams reserve driver Alex Lynn came home a distant third for the Grove-based outfit, only just ahead of current GP3 Series championship leader Charles Leclerc. The Monegasque racer, who made his official Formula 1 debut with Haas during practice at the weekend, was making his debut for the Scuderia.
Russian debutant Nikita Mazepin ended proceedings fifth for Force India, ahead of Carlos Sainz who completed 91 laps for Toro Rosso.
Santino Ferrucci was seventh for Haas, making his debut in F1 machinery. The American teenager is currently competing in the GP3 Series, and scored his first points of the season last weekend.
Pascal Wehrlein spent the entire day in a 2014-spec Mercedes, completing valuable 2017 tyre development testing for Pirelli. The German racer, who scored Manor’s first points in Austria, completed 48 laps for the Italian tyre manufacturer and ended the day eighth overall.
Rio Haryanto ended the day as the lowest of the four full-time drivers participating in proceedings, just behind his Manor team-mate in ninth.
GP2 racers Sergey Sirotkin and Pierre Gasly rounded out the order for Renault and Red Bull respectively, with Gasly in particular completing the bulk of his running in the wet afternoon period due to an electrical issue in the morning.
The Frenchman also ran the latest version of the Halo device earlier in the day, completing 52 laps in total.
