So what is it?

Short answer? It’s AMG’s 911/Jaguar F-Type rival. The rather longer response is that it’s an all-new sports car developed from the ground up by AMG.

With the last pair of SLSes rolling off the production line this month, this is AMG’s first foray into the core sports car market currently occupied by the iconic 911 and the achingly beautiful F-Type.

The car we’re up close and personal with today is the ‘GT S’ (a less powerful ‘GT’ will arrive later in the production cycle), powered by an all-new 4-litre twin-turbo V8 producing a not-inconsiderable 510bhp and 480lb/ft (so think 911 Turbo and F-Type V8S). And yes, that’s supplied exclusively to the rear wheels.

No massive 6.3-litre, naturally-aspirated V8 then?

True, AMG’s history was built on naturally-aspirated V8 excellence, but in recent years the company has proved that you can downsize, add turbos, increase efficiency and still deliver an apocalyptic soundtrack that makes the hairs on the back of your neck stand to attention. The A45 proved that it can do AWD too, so it’s fair to say AMG is a brand on a technological roll right now.

OK, but what does it sound like?

On start up there’s a guttural V8 rumble inside the cabin that’s pure AMG, and from the outside it barks into life with the exhaust baffles open, just to make sure everyone in the area knows you mean business. At tickover it thumps like its legendary ancestors, and when driven hard in race mode it pops and bangs on the overrun. At full throttle you can still hear the V8 pounding over the blast furnace rush of the exhaust. It’s brilliant.

So they haven’t screwed up the noise. Good news. What does it look like in the flesh?

Think truncated SLS in the proportions. The AMG GT S takes the SLS platform and shortens the wheelbase by 50mm and edits the mass of bodywork, reducing the overall length by 70mm. Purposeful stance though: the GT S is still as wide as its big brother at 1939mm. The styling is by Mercedes Head of Design Gordon Wagener, and if you squint you can just about make out the basic shape through the dayglo disguise. It’s pure AMG Mercedes from the front three-quarter, with the long bonnet and cab-back design, and a neat, short rear. It’s simple, uncluttered and even in disguise, very attractive.

So what’s the disguise all about? Is the car finished, and how did you get past security?

The disguise is because the car isn’t ready for its public debut just yet. Apparently the GT S is 98 per cent finished, but speaking to Tobias Moers (AMG Boss, lead driver for today and the reason I’ve not been kicked out by stern men in security uniforms) there’s still some work to do on low grip calibration, and other last-micron finessing. But don’t let the disguise fool you, this car is the real deal. I’m here because busting into 911/F-Type territory is a tough ask, and Moers is clearly hugely proud of what AMG has created. He can’t wait to show it off. That confidence is part of what makes AMG such an infectious brand: these are car people, whose history lies in racing and constant competition to be the best. If it bears the AMG roundel, then it has to be the best it can be.

Before you get into the dynamics, what’s it like on the inside?

Drop in through the now regular door (no gullwings, this is a more ‘everyday’ AMG than the SLS) and it immediately feels like a serious player. Carbon fibre melds with leather and proper, cold-to-the-touch aluminium, all finished with characteristic handcrafted detail and accuracy.

The central tunnel features eight buttons in a reference to the engine configuration: top left is the dynamic control to swap between comfort, sport, sport plus and race, with an additional individual setting which allows you to store your own personalised preferences. The other buttons allow you to override AMG’s optimised settings individually, so should you wish to mess with the suspension, traction control, exhaust and the rest, you simply press the relevant button on the tunnel and personalise your experience.

Our test car came fitted with the optional glass roof, too – which helps with a feeling of space. Dials, graphics and other info-sources borrow heavily from the Mercedes mothership, all personalised by AMG with their own colour palette and graphics. Even the Burmeister stereo is exceptional, something Moers is keen to demonstrate with the help of AC/DC. Which seems appropriate, somehow.

It’s relatively practical too: the GT S is a hatchback which pops to reveal a boot more than big enough to take a weekend’s luggage, or the automotive industry’s ubiquitous benchmark of two sets of golf clubs. But unlike the 911 there’s no occasional seating in the rear. The GT S is a pure two-seater.

Ok, so the stereo’s good and the interior’s well built. What other trick stuff is there?

The car that we have at our disposal today has the optional dynamic package, which adds carbon-ceramic brakes and an actively-mounted engine and gearbox. By mounting the drivetrain on four magnetorheological mounts (two for the front-mid-mounted engine and two for the gearbox at the back) the GTS actively counterbalances its mass when cornering.

Drivetrains are traditionally mounted on rubber bushes, to reduce vibration through the vehicle, but NVH-friendly bushes flex and affect turn-in as the drivetrain weight shifts. By making the mounts active, the car’s ECU is able to stiffen and slacken them as required and the big, inertia-filled lump in the middle of the car can be made to react to driving demands. It’s designed to deliver quiet, comfortable cruising on the motorway, and sharp reactions when you need them.

Ok enough… I get it, it’s clever. But what it’s like on the road?

I’ve now been relocated to the passenger seat, and Moers fires the GT S up with its dramatic grumble. We drive out onto a damp-but-drying Papenburg test facility, initially heading onto the road circuit which features exact replicas of the very worst German roads, scanned and recreated in the test facility.

The GT S feels solid and purposeful. Its impressive ride quality soaks up what is literally the worst road in Germany. We turn off the B-road test route and enter the high-speed bowl, the GTS building speed effortlessly and the familiar AMG engine noise gradually replaced by the hurricane blast of the exhaust note.

We quickly reach our cruising speed of 155mph on the 49.7- degree banking, with Moers enthusing about the lack of wind noise.

After a couple of high-speed laps we relocate to an exact replica of the Hockenheim Ring that nestles in the centre of this huge testing facility. And it’s here that the GT S comes to life. On the drying circuit, the car’s ability to effectively distribute 510bhp through its rear tyres is mighty, as is the predictability with which it breaks away if provoked.

Moers piles into corners ever later on the brakes, and is back on the throttle earlier and earlier as the GT S squats and fires out and onto the next. More drama? Simply apply more throttle earlier, and it’ll drift on demand. Older AMGs were hamstrung by their occasionally recalcitrant gearboxes, but the GTS’s 7-speed twin-clutch fires ratios at the frantic V8 almost instantaneously, up there with the best ’boxes on the market. As the laps accumulate, the GT S’s combination of power, grip and composure deliver devastatingly fast lap times.

What’s clear from our day in this top secret skunkworks is that the AMG GT S is the very distillation of all that’s good, all that we love about the singularity of approach of the men in Affalterbach. The 911 and F-Type should be very worried indeed…

When do we see it for real?

The interweb is rife with speculation about timings for the actual reveal, the most popular theory being around the Paris Motorshow in September. But this is a big car for AMG, so we’d put our money on a more personal launch at AMG headquarters to allow the GT to make headlines in advance of the show.

As for Top Gear’s turn behind the wheel… we’re confident we’ll be in the driving seat of the newest AMG before the end of November. See you then.