What's all this about?

We've had the Mercedes-AMG E 43 4Matic, with its 401hp/520Nm biturbo 3.0-litre V6, but we always knew there was a more potent E-Class range-topper on the way. And here it is. Despite the fact its engine has got smaller again, AMG's latest development holds onto historic badging and is thus the Mercedes-AMG E 63 4Matic+.

What do you mean, 'its engine has got smaller again'?

Ever since the W211 AMG E-Class morphed from a supercharged 5.4-litre V8 (badged the E 55) into the 6.2-litre normally aspirated model of 2007, the hottest E has been losing capacity. That superb 6.2 motor went back to a 5.5-litre twin-turbo V8 in 2011, during the facelift of the W212, and now - despite the misleading '63' badging remaining - it's actually a 4.0-litre V8.

Oh. Is that the same engine as in the C 63, then?

Yes, it is. But don't despair, for a couple of reasons. One, this 4.0 V8 is a belting unit. And two, it might be down on swept capacity in the E 63, but it sure isn't lacking firepower. Because, in its more potent 'S' guise, the E 63 is the most powerful E-Class ever built, according to Mercedes-AMG. This fact neatly overlooks some mental Brabus E-Class creations with 800hp and more, but we understand what AMG means: the most powerful factory E-Class. And that can surely only be a very good thing indeed.

So how much grunt does the E 63 have to play with?

Like the C 63 and the Mercedes-AMG GT supercar that share this 'hot inside V' 4.0-litre unit, there are two derivations of E 63: the, er, 'regular' car and then the frightening 'S' example. Due to AMG's first use of twin-scroll turbocharging - there are two of them in there - the E 63 delivers a magnificent 571hp and 750Nm. You may have noticed the 4Matic+ nomenclature in the E-Class's badging, which of course means the E 63 is all-wheel drive, so that equates to a 0-62mph time of... wait for this... 3.5 seconds. From an executive saloon. That's as quick as Audi's R8 supercar in non-Plus specification. And we bet an R8 owner would be pretty nonplussed to be beaten off the lights by a four-door Merc.

But then there's the S, right?

Oh yes. Ramping things up to the insane level, this adds another 100Nm to the mix and takes peak output to 612hp. The 0-62mph time drops by another tenth to 3.4 seconds and BMW gently weeps into its Bavarian beer, as it desperately tries to work out a way of countering such Benz artillery for the next-gen M5. Either one of these E 63s can do the limited 155mph top speed, with an optional AMG Driver's Package lifting that restrictor to 186mph. But 200mph+ would surely be a cinch for either example of the Mercedes-AMG, without such electronic nannies being in place.

What else has AMG done to corral this power?

The 4Matic+ AWD system is said to be an all-new set-up with fully variable torque distribution front-to-rear. There's now a wet start-off clutch in the nine-speed AMG Speedshift Multi-Clutch Technology (MCT) gearbox, too. The E-Class's Air Body Control system has been comprehensively worked upon to deliver AMG's latest sports suspension, said to offer a wonderful blend of dynamic handling and steering feel, allied to long-distance comfort. And there's a Drift Mode.

Drift Mode?! Like the Ford Focus RS?

Yes, although we suspect a 612hp/850Nm V8 will allow for considerably more rear-axle antics than a 2.3-litre EcoBoost. Activated through the 'Race' programme using the steering wheel's shift paddles, this requires the ESP to be deactivated and the transmission to be locked in manual mode. Meet all these prerequisites and the E 63/E 63 S models become purely rear-wheel drive. Mercy. Drift Mode is standard on the S, and an option on the non-S.

What else does the E 63 have up its sleeve?

The engine has AMG Cylinder Management, which shuts off chambers two, three, five and eight under light throttle loads to make the E 63 into a four-cylinder motor. This ostensibly saves fuel. You'll also notice the subtle-but-muscular exterior styling, featuring front wheel arches flared by 17mm to accommodate the Mercedes-AMG's wider track and 20-inch wheels, massive brakes with meaty callipers, an interior swathed in carbon fibre and some natty AMG-branded sports seats. And a flat-bottomed steering wheel. We have serious levels of want.

When does the E 63 go on sale?

Full release details, prices and specifications aren't confirmed as of yet, but to answer your question, 'not bloody soon enough' would be our response.