Thiriet by TDS Racing led a rain-soaked first practice session for the Silverstone round of the European Le Mans Series.
A 2:08.679s fastest lap by Mathias Beche saw the #46 Oreca 05 Nissan lead most of the 90 minute morning session.
Beche finished 0.555 seconds ahead of the Greaves Motorsport Gibson 015S of Julien Canal.
The two SMP Racing-entered BR01 Nissans finished third and fourth, both within a second of the Thiriet benchmark, while G-Drive Racing completed the top five with its #38 Gibson.
Persistent morning rain had left patches of standing water across the circuit, which led to cars including the G-Drive Gibson, #27 SMP Racing BR01 and #40 Krohn Racing Ligier experiencing off-track excursions.
The 20-strong LMP3 category was also determined by half a second, as French outfit Duquiene Engineering took the top spot with its Ligier JS P3.
2015 GTC champion Dino Lunardi set a 2:13.329s time to go 0.499 seconds quicker than the #2 United Autosports Ligier of Alex Brundle, with the #10 Graff Ligier of American Sean Rayhall ending the morning third.
In LMGTE, Aston Martin and Porsche occupied the sharp end at the end of the session, with the former taking the top spot. The Beechdean-sponsored Aston – driven this weekend by Andrew Howard, Darren Turner and Alex MacDowall – topped the order with a 2:21.752 coming early on.
Howard’s fastest lap put three tenths of a second between him and the #77 Proton Competition Porsche 911 RSR of Mike Hedlund, which edged out the #97 Aston Martin in third.
Free practice two for the ELMS 4 Hours of Silverstone takes place later today (April 15) at 14:45 local time.