Ex-Formula 1 champion Jenson Button was left "smiling ear to ear" after completing his maiden run in SMP Racing's BR Engineering BR1 LMP1 car at Magny-Cours.
Button is set to make his FIA World Endurance Championship debut next month in the Le Mans 24 Hours after agreeing a deal to contest the full 2018/19 superseason alongside Vitaly Petrov and Mikhail Aleshin in SMP's #11 BR1-AER.
He missed last weekend's Spa opener due to clashing Super GT commitments, but he was able to turn his first laps in the Dallara-built prototype at Magny-Cours on Wednesday.
An SMP Racing representative told Motorsport.com: "We are very happy after the first test day with Jenson in Magny-Cours.
"He was immediately comfortable in the car and enjoyed a full testing day, including day and night runs.
"Jenson had a series of long and short stints and extracted most of the car in each run. The car was with the low-downforce aero kit, same as at recent race in Spa as we are preparing for Le Mans."
The Briton's next test in the BR1 will be the Le Mans test day on June 3, two weeks before the race.