There was one question above all I wanted answered the day I drove up to Snetterton to drive the McLaren Senna GTR. It costs £1.1 million before tax and cannot be raced. It is a seven-digit track day car. So why on earth would you not spend just one third of that money and buy a brand new McLaren 720S GT3, which I didn’t imagine would be much slower but in which you could also actually compete?

Of course, part of the answer I knew already. Their markets are completely different, as different as between the Senna GTR and the superfast Radical you could buy for an even smaller fraction of the money. Ultimately, it’s not about how fast you go, but how you go fast. And McLaren Senna customers are not Radical customers and vice-versa. Nor are they GT3 customers either. Or not usually.

“It’s a lot faster than a GT3 car, even when on tyres designed to last”

The Senna GTR customer buys one because he, or she, can. They’re on the list of McLaren’s most valued customers, just 75 of whom will be offered the same opportunity. Many if not most of these cars will be mothballed so you’ll either play with yours alongside like-minded individuals at McLaren track days around the world, or you’ll run it yourself and know there’s scarcely an event you can attend at which you will not be driving the fastest, most dramatic car in the field.

“But surely there has to be more to it than that?” I asked long-time McLaren development driver and racer Rob Bell. “I think you’re going to be surprised… It’s quicker than the GT3 car – a lot quicker,” he said. “We estimate it’ll lap 3-5 seconds faster than the GT3 and that, remember, with a tyre that’s designed to last. If we put it on the same tyres as we use in GT3, the margin would be greater still.”

I don’t know why I was surprised. The Senna GTR engine is not obliged to breathe through restrictors, so the 814bhp output of its 4-litre twin-turbo motor is at least 25bhp higher than that of the GT3. At 1188kg it’s lighter than the GT3, while its bodywork need not comply to any aero regulations, which is why it can develop 1000kg of downforce at 155mph. More power, less weight, more downforce: ergo you have a faster car.

Compared to the road-going Senna it really is a very different animal, far more removed than its predecessor – the P1 GTR – was to the stock P1.

This GTR is 34mm lower and 77mm wider at the front, 68mm wider at the back. The standard Senna comes with super-sophisticated suspension hydraulics that allows it to ride close to the ground on the track and at a relatively conventional height on the road. Relieved of the need to provide this facility, the Senna GTR instead uses conventional double wishbones, coil springs and anti-roll bars, complete with four-way adjustable dampers and solid bushes.

The bodywork and suspension are designed with two goals in mind. First, to produce as much mechanical and aerodynamic grip as possible, second to make sure the car remains aerodynamically stable in all conditions, but especially under heavy braking where the change in the car’s pitch might otherwise seriously affect its balance. It comes with an aggressive front splitter with active aero blades, new front dive planes and vortex generators at the side.

But you’re likely to notice only the enormous rear wing which makes even that of the road Senna look pretty modest by comparison. But its location is as important as its size: it has been thrust rearward, outside the envelope of the car where it would never be allowed on a street machine. Here it combines with the diffuser into what is effectively a single super-efficient aerodynamic element.

The cockpit is very simple indeed, and configured around the fact that a fully harnessed driver wearing gloves and driving a car capable of generating well over twice the force of gravity both through a corner and under braking needs the operation of the car to be as easy as possible. No stretching for some distant switch, because you can’t stretch. No squinting to read an unclear display when the car is already trying to detach your retinas.

The steering wheel is effectively a couple of handles placed either side of a central control bank. Nothing you are likely to want to do while driving requires you to take a hand off the wheel. Usually you need to do no more than extend a digit. Via the wheel you can control the stability systems and the powertrain mapping. You can activate the car-to-pit radio, scroll through your information screens, activate the pit-lane speed limiter and launch control, flash another car and engage neutral. You can also operate the DRS system, which flattens the rear wing, but only when the car is travelling in a straight line and with maximum throttle, so you can’t suddenly rob yourself of all your downforce by accidentally pressing the wrong button at 140mph mid corner. Which is handy.

Information is displayed on a high-definition screen in front of you, which is so clear I’d like to see them in sporting road cars. There is another display in the centre of the car which does the job of the rear-view mirror. It is also here that you can set the air conditioning – a feature very sensibly retained. If I can get sweaty driving it at a cold and damp Snetterton in November, imagine what it would be like in mid-summer at some of the world’s more glamorous race track locations.

The GTR’s voice is very loud – thanks largely to the removal of the car’s second catalytic converter – but it’s not at all nice. Instead it sounds raw, aggressive, intimidating. But at least it remains as easy to trundle out of the pits as any paddle-shift road car: no need to look foolish by stalling it in front of your peers. Like the fact the car is easy to access and exit, this stuff matters in a way that would not apply in a racing context.

“I found myself learning the circuit mostly through the side windows”

Today, Snetterton’s surface is evil. In some areas there is standing water, in others it’s merely wet. Parts are probably better described as damp and as the laps accrue there may even be fragments of a dry line emerging, but it can never be trusted. The only consistency is the fact that it’s cold. So it’s full-wet tyres for me, and I’ll have to leave the cheek-rippling slick options for another day.

Having not been here for a while, the crew sent me out in a road Senna to refamiliarise myself with the track, which I found myself doing largely through the side windows. A car I had loved driving around a dry Estoril last year was busy turning Snett into a nightmare. Even in a straight line it would snap sideways unless you treated the throttle with balletic care and precision.

Which was hardly reassuring. But not for the first time, I found a track car to be far easier than its road-going equivalent. As with all racing cars, tyre heat is the key and the wets were as welcome for their super-soft construction as their chunky tread blocks. Any amount of heat provides more grip, which works the tyre harder, generating additional heat and therefore even more grip. It is a well known circle of virtue in racing terms.

“You block out the intimidating bits; the noise and pulverising thrust”

So the most difficult part of driving the Senna GTR in such conditions was just getting some kind of temperature into the tyres, but when they get warm you can feel the grip coming every time you touch the throttle, brakes or turn the wheel.

And then the Senna GTR – this mad £1.1 million, 814bhp animal of a car – does something very strange. It becomes rather easy to drive. You have to block out the intimidation factors such as the noise, pulverising thrust and your memory of just how untamed this car looks, and focus on what it’s actually doing.

It’s providing you with a supremely stable platform, one that allows confidence to build, even in such conditions. It may not look it, but when it is like this, the GTR is 10 times easier to drive than a conventional Senna. Briefly you wonder if it’s trying to lure you into taking liberties, but even when you do and allow the back to start sliding around, the anticipated mugging never takes place. Sure, it slides quickly, but its actions are so linear and clearly signposted through the chassis you don’t even need to recover it, you can just use the steering to check the slide and ride it out with the throttle.

And this is the point, and the real reason that wealthy clients might consider the Senna GTR worth every extra penny over a GT3 car. It is possible you could look silly in one, but I think you’d have to try pretty hard. By contrast you can look silly in a GT3 car at least twice – getting in and pulling away – even before you’ve reached the end of the pit lane and the track.

More importantly, a GT3 car is designed to deliver a lap time, and everything about it is focused on that aim. You have to drive them a certain way which requires a lot of skill and an aggressive approach: you brake as hard as the ABS will allow all the way into the apex, then trust the traction control as you nail the throttle to the exit. If you’re anywhere between these states, balancing the car on part throttle, wheel gently writhing in your hands as you slide, you’re losing time.

But there are no races to win in the Senna GTR, so the lap time doesn’t matter. It’s the driving that counts and even at this cold, wet, damp and not-quite-dry Snetterton, it provided epic entertainment from first to last, along with the sense that anyone with moderate driving skills could manage it. I can only imagine what it would be like on a hot dry surface. I hope one day I may find out. If I do, I’ll let you know.

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