Sam Bird said he was pleased with a productive start to the three day Young Driver Test at Magny-Cours as Mercedes pushed ahead with a series of developments for the remainder of the F1 season.
The test driver was charged with a running a new exhaust layout on the first day of running at the French circuit, while there was also further work carried out on the rear wing of the car.
In total, Bird completed 95 laps – more than the other two drivers on track with him – and ended up with the third quickest time.
The Briton is back at the wheel for a second day of running today.
"We've had a very productive first day of the test today and were able to complete everything that we had planned on our programme,” he said after Tuesday's running. “It felt great to be back in the car again and I enjoyed every minute of it.
“I've driven at Magny Cours previously in a Formula 3 car and it was good to experience it today in a Formula One car. The layout here is nice and smooth whilst also being quite challenging. We've collected a lot of data today which will take some time to sift through this evening and I'm looking forward to another good day tomorrow."