George Russell kicked off day one of Formula 1's post-Hungarian Grand Prix test at the Hungaroring with 119 laps for the Silver Arrows.
The Mercedes Junior Driver, at the wheel of the W08 beast for the very first time, was fourth fastest on the day, clocking a 1:19.231 on the SuperSoft tyre in the afternoon.
George's first day of testing consisted mostly of aero collaboration work, as well as a vibration logging programme and some brake work.
"Today was incredible - I have been looking forward to this for so long," said George. "It's every young driver's dream to drive a Formula 1 car. As soon as I got on track, I straightaway understood how much grip and downforce this car has got - it is amazing.
"48 hours ago I was driving a GP3 car around the same track, but today was totally different. Luckily for me I had done lots of simulator work with Mercedes, so I knew what to expect.
"The biggest difference is the power steering in the Formula 1 car, and I could feel that as soon as I got out on track. And the braking potential is enormous. I was expecting the speed on the straight and the downforce in the corners, as everyone does.
"I don't think anyone quite understands the braking power of this machine. In GP3 we enter into Turn 1 at about 260 or 270 km/h, braking at the 100 metre board. Today, I was going in at almost 300 km/h, braking 25 metres after what I would do in GP3.
"Today mostly consisted of longer runs with higher fuel loads. We wanted to see the degradation of the tyres, and mainly trying to work for the race simulations.
"I was quite happy with my performance. For my first time in the car, completing 119 laps and not being far from Valtteri - I'm pretty pleased with that."
Valtteri Bottas signed off for the summer break with one final day of testing. The Finn - driving the W08 for Pirelli - completed a massive 155 laps towards 2018 Slick tyre development.