As I throw 2,550kg of high-powered truck into a damp French switchback and feel the nose and tail start to move, it strikes me just how far removed the G63 AMG truly is from the go-anywhere concept that left the designer’s pen back in the Seventies. It also reminded me why this is, without a doubt, one of the most divisive, ridiculous and downright hilarious cars on the planet right now. Lest we forget, the G-Class started life as a military vehicle, the Geländewagen, or ‘cross-country car’ in English. Apparently it was suggested to Mercedes by the Shah of Iran and was first offered for the road in 1979. But even then it was seen as real off-roader, barely concealed military hardware for the masses. It was the German Land Rover Defender. AMG changed all that. In the late Nineties, about the same time it dropped the G-Wagen name in exchange for G-Class, Mercedes’ in-house tuning arm produced what was by some considerable margin the most insane vehicle on the road. The G55 AMG was a total mismatch of chassis and engine, a near nonsense, and it proved a total, runaway success. The Middle East embraced the car like no other region. The wealthy run fleets of them and a G55 AMG was a sign that one had arrived in the world. Now, more than 40 per cent of Gs are AMGs. Of course, with the arrival of the G63 AMG, there will be a tidal wave of customers beating down Mercedes’ doors and, privately, there are fears that the local supply might just not be able to meet demand. Getting to the heart of the big Mercedes’ appeal is a tough one, because it’s a car that simply defies logic, but to drive one is to simply fall in love with the lunacy. Fuel bills be damned, after just a few minutes behind the wheel I knew I had to have one of these monsters in my life. Someday… Even now, the original military purpose is clear to see. Mercedes has updated the shape and yet kept the box-like dimensions intact. In fact, take the modern sheen off the press shots and it would easily look like an escapee from the Seventies, with sharp-edge design, a crease-sharp front end and those massive slabbed sides. It’s like Mercedes has wilfully eschewed progress to keep the spirit of the original car alive, and a twin-blade grille and reshaped bumper with three air inlets are one of the few visual changes. I open the rear and it truly does feel like a bank vault, as there’s something deeply indestructible about the G63. Once AMG is finished it is not a car to go anywhere anymore, but it feels like it could. That tank-like feel starts at its very core, with a body-on-frame construction that has long been discontinued by more or less everyone else in favour of a spaceframe/monocoque approach. Inside, the car gets a new centre console recognisable from other Mercedes models, a TFT screen in the instrument cluster and indeed it’s the interior that feels the most different. It’s more luxurious, the leather is a higher grade and the better-equipped test cars at the launch venue came with lavish quilted leather seats with the usual battery of electrical adjustment. Tuners used to make big money from bringing the interior up to the required standards, now their offerings might just look a touch redundant. This feels like a real luxury car now, with relatively few off-road pretences bar the locking centre, rear and middle differentials. To fully exploit them the car would need smaller wheels and proper off road tyres, and it has to be said that Mercedes is slowly dropping the off-road element of this car in its sales pitch. The diesel-powered G Professional is still a warrior off the beaten path, but that is a totally different animal to this luxury bus with a rocket up its bottom. Because the best and defining part of this car is the 5.5-litre V8 biturbo and the simply silly side exit exhausts. I fire it up and that throaty roar is there from the start, the car even rocks ominously and smoke bellows from the quad side exit exhausts beneath the rear door as I blip the throttle like a naughty schoolchild in the car-park. Never has a car felt so out of place. This is an area populated by real, working, agricultural 4x4s designed to tackle the mountains in the winter snow. And here is a racing car powerplant slapped into a truck, tuned to 544bhp in this particular instance. As the growling Messerschmitt of an engine roars, we all burst out laughing. It just has that effect. This is a ridiculous car, from the beginning to the end, but therein lies its appeal. Cars like the X6M and Audi Q7 seem to try so hard to be cool that it costs them: the G63 Mercedes barely seems to try at all to score a direct hit. We have perfect mountain roads, the snow had melted days before and we’re presented with dry roads — thank the heavens. Because in the wet, on these tight, twisting, wall-lined roads, this car could be a recipe for disaster. In a straight line, though, it is simply epic. It slams to 100kph in 5.4 seconds, which is insane for more than 2.5 tonnes of car, and with the help of the AMG Speedshift Plus 7G-Tronic seven-speed gearbox it will hit 200kph. Would I want to? On an arrow-straight road with nothing blocking my path? Yes… Because there’s just something so utterly addictive about the way this car gathers speed, especially with the auto ’box working wonders and dropping three gears when I flatten the throttle from a crawl — the typical overtaking move then. Perhaps it’s the way the car overcomes impossible odds and makes a decent fist of dragging in the horizon as the soft suspension wallows and bounces. There’s a real feeling of smashing a road into submission with a simple application of throttle and to thoroughly explain the satisfaction behind the process would delve deep into the weirdest corners of a man’s mind. I’m happy to simply accept it is outrageous fun. To get the best from the big AMG, you have to switch out of the inappropriately named Eco mode, though. Fuel economy and taxation are big considerations in other parts of the world and it’s at least noble that the new G63 comes with stop-start tech and improved fuel efficiency over the outgoing model thanks to direct injection and an intelligent alternator, but you have to wonder whether the  customers are truly concerned about the environment in a car that emits 322g/km of CO2. The gearchanges that stretch out for an eternity and the lack of revs in Evo mode will matter, though, and they won’t make anybody happy. Put it in Sport and things improve. You can even go for full manual control of the gearbox with paddle shifters behind the wheel, but even cranked up the manual changes feel slow, ponderous and artificial. I soon dump it back into Sport and let the gearbox do the work. Even this car has its limits: a racing car it isn’t. Of course piling on speed means you have to get rid of it too. And though the brakes on the G63 AMG are monsters, 375mm discs and six-piston callipers on the front and 330mm rears with floating callipers do their best, but there’s that sweating, nervous sense of imminent disaster every time I really shove the brake pedal. And as one mountain bend tightens on me a little more than I expect and I have to really go for the middle pedal mid bend, I realise trying to hustle the car is a total crapshoot. It’s the weight transfer that is unnerving, and doesn’t really work. I can feel the traction control, which you can never truly switch off, invading on almost every bend to keep the car in a straight line and as the confidence grows I can feel 2.5-tonnes subtly fishtail through every hairpin as the electronics sort out the physics-busting demands going on underneath. With a steep drop on one side of a narrow ribbon of tarmac, and a solid wall on the other, that’s proper scary. And I soon back off and settle for slow in, fast out, and no gigantic repair bill. Driving this car recklessly in hairpins is to miss its point. It is barnstormingly fast in a straight line and can hound most real sportscars down the road thanks to its groundswell of 760Nm of torque. It will also win the traffic lights Grand Prix with a ridiculous amount of cars, but its real skill is simply to own the road with the high seating position, the vast expanse of real estate and the ludicrous power. Those with a G63 in the fleet invariably have other, more focused, cars. The G63 is about effortless performance. It is the King of the Road, and in this new form it’s hard to see anything challenging its position at the very top of the SUV food chain. Almost… Because Mercedes has muddied its own waters with the launch of the even more incredulous G65 AMG. With the 6.0-litre twin turbo pumping out 612bhp and 1,000Nm of torque, the G65 will immediately become the one to have in the badge conscious Middle East. We could not drive the new-range topper, which will cost €264,000 (Dh1.2 million) in Europe compared to the G63 AMG’s relative bargain price tag of €135,000. It doesn’t sound as good, as the twin turbo V12 always sounds flatter than the V8, but on price and pure performance it is the one to have. So Mercedes hasn’t just launched a new king of the road, it now has two. Even though the 63 is more than enough, part of me wants to throw the bigger 65 into a switchback bend just to feel the sheer insanity again.