"On track it would change up a gear on its own. They didn’t have automatic downshifts because it would upset the balance of the car. You had a pre-selector, where you could downshift five gears on the straight and, when you applied the brake, it went down five gears for the corner. It was a lot like a computer game, but it was an incredible car.
"It was pretty embarrassing at the time, as one day I turned up at the test, put the helmet on, fired it up and there was no clutch paddle. So I got on the radio and yelled, 'There’s no clutch paddle!' and the team said, 'Oh yeah, sorry. It’s now a button'."
Gary is in hysterics at this point, as are the rest of us hacks gathered around a table in the canteen of Mercedes-AMG's Affalterbach headquarters. I'm still pinching myself that I'm having lunch next to a guy who's tested every significant car from the pinnacle of motor racing over the past 15 years.
I'm even more impressed at his humility and self-deprecating humour, as he comes across as just 'one of the lads' throughout the entire day. He continues...
"The V10s were pretty extreme cars. I remember my first F1 test in December 2000 at Jerez. I did about 14 laps, got out of the car and my neck was finished. It was hanging off. So they got the foam pads out, stuck them on the side of the cockpit and sent me out again.
"But that’s how it was back then. The g-force in those days was incredible. Owing to the amount of power the V10s had, they needed massive wings and massive amounts of downforce to go with the 950bhp engines. Then we changed to the V8 which, to start with, was a bit of a toned-down V10, and a bit slower.
"To start with, we would blow up two or three engines every test, which was the kind of thing you got used to. You’d learn the sound of the engine about to expire and you’d be on the straight close to the rev limiter and pull the clutch paddles in before it went pop, so you didn’t get fired off into the barrier.
"A couple of times I had it happen at Jerez where the engine let go. You’d go to pull off to the side, the gearbox would lock and you would be fired off into the barrier, so you learnt the sound before it would let go."
At this point I just sit back and let Gary continue. His enthusiasm is unrelenting.
"In 2009 we started with KERS and that headache. I remember the first test with that car and the team were like, 'Right, KERS is on this button, and then there’s this button to do this...'. I just thought, 'I can’t drive this; there are too many things to do!'.
"The problem at the time was, as soon as you got on full throttle, you were trying to get KERS, and you were looking at the dashboard because they wanted you to use 10% out of this corner and 7% out of that corner, and you were forgetting to change gear.
"However, once you got used to that and all the procedures, then DRS came in as well. And then you had the magnificent f-duct system, where you placed your elbow into the hole in the side of the cockpit and changed the car's aero to reduce drag. It was a great innovation, but some of the things were really quite challenging.
"Recently, the most incredible F1 car was the 2011-2012 version with the blown diffusers. The amount of downforce they had was phenomenal. In qualifying modes, the throttle bodies were open 90% through the whole corner.