GT R. If that's a name that sounds familiar, it's because you'll normally find it attached to the boot-lid of Nissan's fastest road car. But it's also now attached to the most potent Mercedes-AMG.

Mercedes-AMG already has a GT model — which we drove last year — which was made one better with the hotter GT S. But what do you follow that with? The GT R of course.

That's R for race. And, appropriately enough, we were at Silverstone race track to celebrate the 50th Anniversary of Mercedes' high-performance AMG brand. Having already sampled the new GT C (that's C for convertible, by the way), and been going rather sideways in an E63S, the GT R — in its unmistakable "AMG Green Hell magno" paint scheme — is definitely the main event.

What is it though? Based on the regular and not exactly under-endowed AMG GT coupe, the GT R is a car that Mercedes is keen for us to attach the #beastofthegreenhell hashtag. That's because it was extensively developed at the Nurburgring — the German race track, nicknamed the Green Hell by Jackie Stewart back in 1968.

The AMG GT R uses a new 4-litre V8 engine complete with turbo-charger, as found in other AMG models. Except that in this version, AMG has thrown new compressors, wastegates, exhaust ports and an ECU tweak at it, boosting the power to 585hp. That's all fed through the fat, 20-inch rear Michelins, via a lightened, carbon-fibre propshaft.

AMG GT R image 3

And carbon fibre features extensively throughout the rest of the GT R — the roof is made of it, as are new wings, the latter which are wider than on the regular GT and account for the GT R looking that much meaner in this guise. There's a racecar-like underbody bracing structure which is made of carbon fibre too. Which all helps the GT R to shed 15kg in weight compared to a regular GT, all the while being a much stiffer, faster car.

That race pedigree doesn't stop at the engine and bodywork. Many suspension components are made from stronger and lighter forged aluminium, the car rides via adjustable coilover springs, and uses adaptive dampers (of the kind you'll find on race cars). And you can't claim racing influence these days without talking aero — which the GT R has in abundance, including an active rear aerofoil that extends 40mm at high speed, sucking the car to the road.

The GT R features active rear steering too, which allows the rear wheels to toe-in up to 1.5 degrees in the same direction as the front wheels at high speed (and in the opposite direction at low speeds) helping turn-in and manoeuvrability.

Finally, the 7-speed auto gearbox has been re-worked with different drive ratios and new software which makes it change faster.

Which all sounds lovely, but it's to actually drive the GT R that we get a real feel of what all this means. Race boots on, helmet on, and it was time to channel our inner Lewis Hamilton and get out and see what this beast of the Green Hell is made of, on Northamptonshire's own Green Hell — Silverstone race track.

True to form for an early August day in the UK, it's raining, and the track is greasy only two weeks on from the British Grand Prix. The AMG GT R feeds 585hp through its rear wheels. It's worth £142,365. And there were only two of them available on the day. No pressure then.

AMG GT R image 4

However, despite the race-car spec, Mercedes knows its market well. Stepping inside the GT R you'll note this is not the same approach as a stripped-out Porsche GT-3 RS. There's no visible roll cage. Yes, there are bucket seats — but they're comfortable and covered in Alcantara. The wide, rising centre console you'll find in all AMG GTs is still here, too, replete with its full complement of buttons. Even the loved-by-some-and-hated-by-others floating iPad-like centre screen is present and correct, along with the Comand scroll wheel and touch controller.

In fact, save for the Alcantara trim, some colour flashes and different dial face graphics, the GT R is just like a regular AMG GT. It might have race car pretentions, but for those lucky enough to have a GT R on order, the cabin has the "usable everyday luxury" box well and truly ticked.

The one standout R-based element is the yellow knob on the console. It's small with the ominous letters "TC" on it. It becomes active when you turn the stability systems off, and allows you to tweak the level of traction control intervention. Given it was wet, we left the stability systems well and truly on. As one of the Mercedes' instructors blurts off the cuff: "it'll have no qualms in throwing you off the track backwards if you mess with it". No fear then.

A thumb on the starter and the GT R doesn't disappoint. AMG models have never been shrinking violets, but the bombastic eruption from the GT R's exhausts on start-up had the entire pit-lane swivelling their necks.

We rumbled out of the pits, and as we joined the track, squeezing the throttle gradually harder, the GT R felt like it was straining to be let off the leash.

AMG GT R image 9

Silverstone might not have the elevation and real weather challenges the Nurburgring does, but it's still famous for patchy weather. It can be raining at Stowe corner and dry at Copse. Tentatively threading the car through Maggotts and then Beckets corner, the GT R felt much sharper than the GT-C we had tried earlier in the day. And as we accelerated out of Chapel and down Hangar straight, all hell breaks loose when the GT R digs those fat rear tyres in, finding grip where there hadn't been any earlier in the day, and blasting us past slower cars on the track as we piled down the straight.

Those slower cars? Just a Mercedes C63 AMG and an A45 AMG. Hardly cars that, in a regular sense, you'd ever call slow. The GT R makes them feel like they're travelling backwards.

There aren't many options you need to spec on the GT R, but one you'll want to consider if you're planning track time is the carbon ceramic brakes that were fitted to the car we drove. These units need careful treatment (you can crack the discs if you don't heat cycle them properly). But at the end of Hangar straight, when bringing the car down from 140mph, the stopping power they provided was awesome. We applied the brakes too early and actually wiped off too much speed. But these brakes just kept on giving all the way around the track, where regular steel discs would have been wilting.

The steering is enjoyable; it's not got the last word in feedback but it's very well weighted, so we feel the GT R turn-in more keenly than any other AMG we drove on this track day. It's very quick, so when the inevitable wet patch of track is found and the car momentarily jinks sideways, an instinctive stab of opposite lock can counter it.

AMG GT R image 5

The gearbox is worthy of note too — it is much faster and more responsive than the unit found in regular AMG models. The lesser models tend to have quite a soft, slow change up at the limit and refuse to change down if that down change will put you within a couple of hundred RPM off the red line. Not so the GT R, which simply whip-cracks up through the gears with a jolt, and bangs down gears, bringing engine revs right up to the red line. Not once did we pull a paddle and have it fail to execute the command.

But it's the sheer performance of the GT R — this thing goes 0-62mph in 3.6 seconds, so we reach 150mph down the pit straight — that stands out the most, because of just how alive it feels. Despite appearing like a scary beast — the bark and bangs from the exhaust adding to that sense — the car seems to complement, to flatter. The sheer smile it put on our face around Silverstone is what makes it memorable.

Back in the pits, the GT R ticked and hummed as it cooled down after our four lap run, and its looks continue to grab attention. Of course, the green paint helps, but this is a proper muscle car — in the truest sense — which looks like a hardcore muscle car prepped for circuit work.

Sadly, we don't get to drive the GT R on the road. But after time with it on the track it's fair to say it's a car that excites and got under our skin in equal nature.

AMG GT R image 7

Notably, the GT R is a Mercedes at the end of the day — which means it would in all likelihood be easy to live with on a day-to-day basis on the road. Although if you don't want to attract attention we recommend going for selenite grey rather than Green Hell; or failing that perhaps just an altogether different car!

So is the AMG GT R the best of all worlds? Well, its competition at this level is fierce — McLaren, Porsche GT3, Audi R8 and even entry-level Ferraris are within reach.

If your name's one of the lucky few down on the list for the forthcoming Porsche 911 GT3 RS, then don't cancel your order. But if you're not? Well, the Mercedes AMG GT R may be just what you are looking for. It is one (green) hell of a car.