(Bloomberg) –Andy Wallace would make a great secret agent. At 147 pounds and average height, the mild-mannered, fiftysomething Brit could have come straight from central casting for the term “nondescript.”

But he’s anything but normal: Wallace has driven and raced high-performance sports cars since 1988, and he’s won more than 25 international competitions, including all four of the big ones: the 24 Hours of Le Mans, 24 Hours of Daytona, 12 Hours of Sebring, and Petite Le Mans 1,000-Mile race.

His day job now is the official test driver for Bugatti. And in September, he set a world record for speed by driving a Bugatti Chiron Longtail to 304.77 miles per hour on the Ehra-Lessien test track in Lower Saxony, Germany. Built during the Cold War, the track was located there because it was a no-fly zone west of the border between East and West Germany. That meant prototype cars built by German automakers could be tested on the track without the risk of spies. Today, Volkswagen AG uses it to test cars from its current stable of brands: Audi, Bentley, Bugatti, Lamborghini, and Porsche, among them.

After a year of preparations in secret, weeks at the test track, and an intensive four days at Ehra-Lessien touching 299 mph, but unable to break the 300 mph barrier, Wallace finally hit 304.77 mph on one last, record-setting lap. The 12-mile track is a three-sided layout that uses banked corners, so he got up to speed on one of the long, back straight stretches.

Bugatti showed the record-breaking car in a warehouse in Los Angeles on Nov. 19. Wallace was there, happy to talk about what driving 300-plus miles per hour does to your body and how he celebrated after his record-breaking run.

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Here’s a condensed version of our conversation.

OK, Andy, be honest. We all think that we could drive 300 mph pretty easily if we had the right car. It’s just a matter of keeping your right foot on the gas, right?

[Wallace laughs.] Well, speed is a linear measurement, but it’s not somehow. For instance, no matter what country you live in, for most of us, even in Germany, 150 mph is a fast speed. And if you take that as a fast speed to 180 mph, although it’s only 20% more, it’s such a completely different world driving at 180 mph from 150 mph. If you then follow that all the way up, when you get to 300, it’s not double 150, it feels like four times or more.

So in terms of driving the car, if you jumped in the car and tried to do it there straightaway, I think you’d go crazy [trying to process the speed at which things fly by while also trying to maintain control of the car].

What’s the speed at which you start to notice this exponential change?

It changes depending on what car you’re driving and what its top speed is, but I always think 150 mph is a big number.

OK, so how do you prepare for that crazy amount of change? You’ve been a pro driver for 40 years, but this sounds next-level.

Yes, unfortunately, you don’t do 300 mph a lot of times [even as a race car driver]. We are always doing it in increments. All of our cars are limited to 261 mph, so first I drive a standard Bugatti with the limiter removed. The first time you do that, when you go a bit more than 261, it’s such a shock. Your [brain] can’t process [the raw speed].

How does that feel once you finally hit it?

Everything is coming toward you. And you’re steering, in control of the car, so it better do everything you ask it. And then once you’ve done that a few times, your brain gets a little bit used to it.

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Where do you feel it most in your body?

Here, in your core. Acceleration is really felt in the torso. It moves around some of your internal organs, it scrambles them [pushing them back and compressing them inside the body]. Obviously the acceleration subsides as you get close to v-max [maximal velocity].

And it’s not like you’re just sitting there along for the ride.

There were so many things to do in the car—I wasn’t just sitting going along for the ride! You’re controlling the car, checking the speed, checking for danger. Trying to keep in the center of the three lanes. And that isn’t as easy as it sounds, because the road is very well used. It’s got a lot of ruts, and the car moves around because you’re going so fast.

The weight of the spinning wheels—the gyroscopic effect of those wheels turning—actually overpowers the steering. It’s a problem that has not been solved because it’s not necessary to solve it normally. But you then get a situation where there’s no self-centering on the steering anymore, so when you have to make an adjustment to stay straight, that adjustment pulls the car over and doesn’t stop, and then you need another one to come back. It’s very small movements, but you’re forever doing that to try to stay straight.

So, yes, your mind is full of lots of things you have to do rather than just absorbing the experience.

During the early part of that run, could you tell you had a winner on your hands?

Yes, I could feel it. You map off landmarks in your mind, so there was the place where the guys were standing. I would always pass them normally at around 430 kmp (267 mph). This particular time I went past them at 438 kmp. So I already knew, “OK, this is going quite well.”

And then another landmark—there’s a surface change, and I went over that faster than ever before. And there’s a radar on the straight that I passed well, and I thought, “Great, this is the run.” So I stayed [with the accelerator pedal pushed] flat out.

What was your immediate thought at that point?

You’re immediately looking for the other end, because there’s a banked curve at the end of each side of the track. It’s a banked track 12 miles all around, and you need to judge the right time to give up on it because the speed is still climbing, you never actually stop accelerating. And you need about a mile to get back down to 125. So there’s a lot to think about. It keeps you busy.

What a thrill. Does it make you hungry for speed at all times?

After I did the 304 mph run, for the next week I drove everywhere at 10 miles under the limit. It was just a relief not to have to drive fast anymore!

It’s a funny thing: When I’m not at work, I very rarely speed. First, I don’t feel the need. You have to do it when you’re at work all the time, so it’s almost a relief [not to]. But also there are so many points of danger on the normal road, particularly if there are people walking about. I’m quite happy just monitoring everything.

I’m not a serial speeder—70 miles an hour is fine.

Do you have to watch what you eat before doing this?

In a Formula One car, you’re braking and accelerating going through corners, so weight is important. For this in a straight line, the weight doesn’t dictate the speed. The only thing the weight does is put more load to the tires. I mean, they didn’t come and sit with me at breakfast and say, “You can’t have that egg.”

I’m 67 kilos. The car weighs 1,900 kilos anyway, so percentage-wise, it’s not so much.

What about alcohol? I know a lot of drivers don’t drink beer or wine, that sort of thing.

I would never drink alcohol before the drive, even two days before. One of the reasons is it messes with your heat exchange system. So if you’re in a hot racing car, it’s a massive no-no. But yes, I do drink. In fact, when we did the winning run, we came out of the test track, went down to the gas station about a mile away, and just all cracked open a beer in the car park. It was great.