Relentless. That's the best single word that can describe the sensation when you firmly depress the accelerator pedal of the Mercedes S65 AMG. Other terms that come to mind include apocalyptic, locomotive and unnerving, all balled up in the back of your throat emerging as a single word when pedal hits carpet and that word is "****."

Even the most civil of you will swear like a sailor the first time you try this. I defy you not to. After the profanities comes a burst of laughter borne of sheer disbelief. Did this thing really just do that? Did two and a quarter tonnes of Swabian steel just bludgeon its way to 60mph in 4.2 seconds? In the interests of journalistic integrity, I feel it's incumbent upon me to try again just to make sure. If power corrupts, 612bhp can do a lot of corrupting. The local police don't seem interested in letting me have a third go.

Let's make one thing clear. There are 63s and 65s when it comes to AMG engines and they are very different beasts. This engine isn't of the latest generation high-revving normally-aspirated ilk, as Mercedes has seen fit to install in the latest CLK 63 AMG. Those engines develop just over 510bhp from their screaming V8s. This is the older, twin turbocharged V12 unit that's a far costlier piece of engineering and requires only the merest few degrees of flexion in your right ankle to dump over 1,000Nm of torque to the rear tyres.

Even the vast 19-inch tyres at the back can only do so much when confronted with this industrial level of torque and the S65 AMG relies heavily on its electronic control systems to keep things in a broad approximation of equilibrium. I once had an opportunity to drive this engine (albeit in a different Mercedes model) with the electronic aids switched off and it was an experience that in five minutes must have aged me five years. No matter how often purists grouse about the stability control and the traction control interfering with the driving experience, believe me it's preferable to the alternative.

"There are people who can't persuade NASA to strap them to one of the shuttle's solid rocket boosters and want the next best thing"

That we're talking about purity of response in a car this big is a testament to the fundamental rightness of the S-class chassis and long has it been thus. Even the last generation S-class was a great car to hustle up a twisty mountain pass and this latest series is better again, the S65 AMG being possibly the quickest way to transport five people and their gear across Europe without your wheels leaving the ground.

Tyre contact is optimised by AMG sports suspension with the frankly astonishing Active Body Control system. The active suspension virtually eliminates the body movements that occur when moving off, cornering and braking. Bends are negotiated with far less roll; the body roll caused by fast evasive manoeuvring is effectively suppressed. Compared with the previous model, the second-generation Active Body Control is even more effective at, for instance, reducing body movements in any given driving situation. The S 65 AMG is one of those cars where you occasionally need to check the speedometer through corners because you're often going a good deal faster than you expect. The usual cues of pitch and roll are almost entirely absent. It's eerily effective.

It's not all clever engineering under the skin either. The interior needs some sense of occasion when you're paying this much and the first thing drivers will spot is the big AMG logo in the instrument cluster's central display. The separate AMG main menu integrated into the instrument cluster displays the currently engaged gear and recommended upshifts in Manual mode, Plus either the engine oil temperature or the battery voltage as well as the RACETIMER. This does exactly what it purports, allowing the driver to record lap times on racing circuits for instance, storing not only the time for the fastest lap but also the average and top speeds as well as the lap length. All the information can be called up using the thumb-operated buttons on the AMG sports steering wheel. Just don't lend the car to an over competitive colleague. Things could get costly.

As well as burr walnut trim, there's also leather upholstery along with the AMG sports seats and that AMG ergonomic sports steering wheel with its specially sculpted rim and aluminium shift paddles. One of the most eye-catching features in the interior of the S65 AMG is the analogue clock with its "IWC Ingenieur" design in the centre console. AMG door sill panels are also fitted as standard.

There are also signature AMG touches on the exterior to distinguish this from humbler Benzes although not so much as to draw unwelcome attention. At the front, the redesigned AMG front apron with enlarged air intakes features a pair of two slanted struts and integrated round fog lamps set in chrome rings. Subtle side skirts meld beautifully with the S65's swollen rear wheel arches to give the car a shapely profile. "V12 Biturbo" lettering on the front wings and multi-piece 19-inch five-spoke AMG alloy wheels with a star on the centre of the wheel painted in titanium grey are also giveaways. A redesigned rear apron and the AMG sports exhaust system comprising two combined twin tailpipes are a finishing touch.

It's always hard to judge one of these monstrously powerful Mercs with a truly objective eye. Most reasonable people would concede that 612bhp is possibly overkill but there exists a market for saloon cars for people who can't persuade NASA to strap them to one of the shuttle's solid rocket boosters and want the next best thing. The S65 AMG is that thing and, in that context, the £145,365 asking price will represent solid value for a privileged few.

TOP 1 S CLASS DEALS

The results below show the top S CLASS deals on buyacar

	Mercedes-benz S Class S65L 4dr Auto Bi-Turbo AMG Saloon
	ETR	Mthly	Saving £13,029	Price £136,021