That permanence is important. There have been various S-class models over the years but, unlike with other cars, the arrival of a new model hasn't rendered the previous one passé. They don't so much get old as mature. And now there's an all-new S-class, just as the last one, launched in 1998, seemed to be getting into its stride.
You can see the new one before you now. The last S-class was an understatedly handsome car. Gravitas and discretion met in one confident package. Its style was as close to timeless as car styling ever is; it was the epitome of the boss Benz. So what has happened now? The new car - Mercedes calls it W221 within the walls of its Sindelfingen nerve centre - has gone all mortal on us, and has adopted the clothing of a transient object. I'm sorry, but those vast wheel-arch bubbles are just too flashy for an S-class. They're embarrassing.
Then there's the bootlid, kind of Maybach-meets-BMW's 7-series in the way it sits on, rather than in, the bodywork. It's mould-breaking and attention-grabbing, but that's not how an S-class should be. It should rise above that sort of sensationalism, above the sudden sense of uneasy flamboyance that has swept all of Mercedes-Benz's new models. It works for the radical CLS four-door semi-coupé, whose roofline the S-class echoes, but it's not quite right here.
That said, the new S-class is more of a looker than its boxy ancestors of the mid-1960s and 1970s. Maybe it's trying to regain a flavour of the 1959-68 "fintail" models. If that's the idea, the style solecisms are partly forgiven. Besides, the new S-class has a good reason to draw attention to itself, because it's one of the most technologically dense cars ever.
It can work out exactly how hard your emergency stop has to be, so minimising the likelihood of another car crashing into its tail. It does this with the same pair of radar beams - one long-range and low-definition, the other short-range and more focused - that also informs the "active" cruise control which automatically slows you if you come up quickly behind a car. Normally, a brake-assist function simply applies the brakes as hard as possible if it senses that you are panic-braking, but this one adapts itself to what is really happening.
More technology (admittedly optional, like the last bit): meet Night View Assist. When you drive on dipped beam, you can't see as far ahead as you can on main beam. But with NVA you can, by means of a screen where you'd expect the speedometer to be, its image provided by an infrared beam and a camera concealed inside the windscreen.
So what happens to the speedometer? Normally, you see what looks like a standard-looking dial except that it's actually a facsimile created on a high-resolution screen. All new S-classes have that. Switch to NVA, though, and the infrared image that occupies the speedo-space is underscored by a bar-graph speedo strip instead. Now we move our eyes towards the Merc's middle, and see another hi-res screen. It contains, among other things, the usual sat-nav and stereo displays.
Just ahead of the centre armrest is a large, round knob which you can turn, press and prod in various directions, your hand supported on a padded rest which itself lifts up to reveal the built-in telephone. Sounds suspiciously like BMW's iDrive to you? Yes, but thanks to massively better on-screen menus and nearby buttons to give direct access to oft-used functions the "Comand controller" works very well. You can even use it to alter the shape of your seat, by means of a 3D graphic which lets you select the part you want to pump up or deflate. There's also an optional massage function and "dynamic multicontour" system which pumps up parts of the seat to support you better when accelerating, braking or cornering.
Related to this is part of the enhanced "Pre-Safe" system which pads out the right part of the seat in preparation for the accident the S-class's sensors divine that you're about to have. The ability to move seats to the best position, close windows and pre-tension the seatbelts is carried over from the old model.
I could go on about the technology within the S-class: active damping for the air suspension, optional active springing to keep the body level, a floorpan pressed with random dimples both to make it stronger and to damp out resonances, and so on.
But let's turn to the interior design, visually more satisfying than the exterior. Thin bright-metal strips underline the wood, and from behind those strips emanates a gentle light at night (controllable on "Comand" ). Most switches are metallic, there's a square, watch-like clock between the centre facia vents and, in long-wheelbase S-classes, the rear seats recline (as they have done for years). This time, though, there's more room because the new S-class is markedly larger in all directions than the last one.
The scene is set, then, for a serene drive. But I wasn't prepared for just how serene it would be when I set off in an S500, the only model in the range to have an all-new engine. This V8, actually of 5,461cc, delivers a rousing 388bhp and propels the hefty Mercedes to 60mph in 5.3 seconds, yet uses less fuel than its 5.0-litre predecessor. Other engines range from the S320 CDI V6 turbodiesel (replacing the old S-class's straight-six, already seen in other models and destined to be the biggest seller) through the S350 V6 to the twin-turbo, V12 S600 with 517bhp. This last engine has colossal torque (612lb ft compared with the S500's 391), sufficient to hurl it to 60mph in 4.5 seconds.
Moving off is ultra-easy. The automatic transmission selector lever is on the steering column. There's no complicated pulling and guiding, unlike the superficially similar system in the 7-series; this an ergonomically transparent car. The transmission itself has seven forward gears, and you can control them manually by push-buttons on the back of the steering wheel's spokes.
Not that there's much need of manual intervention, so casually muscular is the engine. You can hear its V8 woofle when it's roused, a woofle attenuated by slightly different phasing of each cylinder bank's valve timing to even out the exhaust pulses; but when you're cruising, the S500 is as silent a car as I have ever encountered. It would be easy for the driver to feel cut off from the world in such a car, but there's a connection to be made if you want it. Such is the effectiveness of the Airmatic DC suspension that this behemoth of a car feels accurate when rushed through corners, the ample forces it generates all acting in the right direction, the steering weighted perfectly.
There's no heaving or lurching even when the suspension is set to its usual comfort mode. Switch it to sport, and the ride firms up, but not to the point of destroying the S-class's ability to finish off what an unconscientious road-builder started.
This is a very impressive car, one that puts Mercedes-Benz back on top as the maker of the world's best real-world luxury cars. It has taken a battering recently for letting quality standards slip, but this new S-class is proof of a fight back. UK sales start in December, with prices ranging from about £51,000 to £99,500.
The new S-class is the eighth in a dynasty that goes right back to 1954. Here's the bloodline with some very confusing numbers:
1954-59: 220 SE
The Ponton was Mercedes' first car with a unitary-construction body, and sold strongly in shorter-bodied, smaller-engined versions (including diesels). Six-cylinder SE was faster and more luxurious.
1959-68: 220 SE - 300 SE
The Fintail range again stretched from diesel taxis to lavishly chromed S models. This time the E denoted Einspritz (fuel injection). The speedometer resembled a vertical thermometer.
1965-72: 250 S - 300 SEL 6.3
Where did the style go? This S-class was a little more different than before from lowlier Benzes, and offered a V8 engine in the top models. The multifunction stalk (wipers, indicators, dip) made its debut.
1972-80: 280 S - 450 SEL 6.9
Now the S-class is a completely separate model, larger with horizontal headlights and ribbed tail-lights. The ultimate 6.9-litre V8 was a real tyre-smoking hotrod.
1979-92: 280 S - 560 SEL
Style is back with a highly elegant S-class, the first car to feature traction control and pictogram buttons for its electric seats. There was a long-wheelbase version too.
1991-98: S280 - S600
Style disappeared again with this slab-sided monster, timed perfectly for a world economic downturn. Its onslaught of technology included double glazing plus self-closing doors and boot. Delightful to drive.
1998-2005: S320 CDI - S600
Briton Steve Mattin styled this one, the best-looking S-class since the Fintail: smaller than the previous one outside, bigger inside, and now with a diesel option. Too many buttons and switches, but a great car.