• Like the coupe, the design of the cabriolet is superb. Picture: DAIMLER AG

  • The interior is typical S-Class luxury but that rear legroom might be a little cramped. Picture: DAIMLER AG

  • Drop the top and it’s all about glamourous cruising. Picture: DAIMLER AG

  • The multi-layer roof provides plenty of sound insulation. Picture: DAIMLER AG

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THE Mercedes S-Class coupe has charmed just about everybody who has driven it, and the cabriolet version is likely to do exactly the same. It looks good, drives beautifully and is utterly composed and balanced. This, and its hard-topped brother, would be close to the best Benz on sale today.

If you were born the last time Mercedes launched a convertible version of its S-Class limousine, you’d be 45 years old. Now Daimler’s heir apparent, Ola Kallenius, has decided the time has come to spread the S-Class’s footprint again.

And so there is now an S-Class limousine, a longer S-Class limousine, an even longer S-Class Maybach limousine, a getouttahere-long S-Class Pullman, an altogether lovely S-Class coupe and now, finally, the S-Class cabriolet.

The cabriolet is based on last year’s biggest surprise packet, the coupe, and it’s equally surprising and equally high class in everything it does, and everything it projects.

It borrows heavily from the S500 coupe, including lifting the entire 4.7l V8, rear-wheel drive powertrain, and fitting it beneath its open-topped bodyshell. That gives it 335kW of power and 700Nm of torque, and even though it’s 85kg heavier than the coupe at 2,115kg, that’s plenty of gristle. It gets the big, four-seat convertible to 100km/h in a claimed 4.6 seconds and is limited to 250km/h, which it gets to rather quickly.

Then things get silly over at AMG, with the 5.5l twin-turbo V8 adding 430kW of power and 900Nm of torque into the mix, though it swaps out the S500’s nine-speed automatic for its own seven-speed unit to cope with the added torque. Plenty of urge, then, and it hits 100km/h in 3.9 seconds, though only as an all-wheel drive (it’s 4.3 seconds as a rear driver) and has the same 250km/h top speed.

The cabriolet borrows all of the S-Class’s safety and driver-assistance systems (which would run to about 1,500 words alone if we listed them here) and adds pyrotechnic (explosive-driven) rollover bars that shoot up from behind the rear seats. That’s to allay fears of body flex creeping into the 5,027mm convertible, and they’re fears that were well founded. Most things with this big a hole cut into the top will react poorly when torsional forces are shoved into them.

Benz has done such a good job of shoring up the underbody of this one, with reinforcing beams beneath the cabin, in the rear structure and under the bonnet, that it feels only a bit less rigid in the body than the coupe. There are multi-link suspension systems at both ends, the car runs continuously variable, adaptive dampers as standard equipment and big brakes, plus 245/50 R 18 tyres all round.

They’ve worked even harder over at AMG with the S63 getting its own tune of the Airmatic air suspension system, more camber at both ends, a thicker front anti-roll bar and a stiffer rear sub-frame. It can even raise or lower its ride height by 30mm, though the car will lower it again automatically in Sport mode, or when it exceeds 120km/h.

Benz claims an astonishing coefficient of drag figure of 0.29, and that’s with the roof down. There has also been some underbody reinforcing to go with its aero-enhanced floor and slippery three-layer cloth roof. Calling it a "three-layer" cloth roof understates the work that’s gone into it, and it’s probably closer to six layers once you take the different material mixes into account.

The S500’s engine is initially calm, but with a deep burble to it, and it’s strong and willing. You won’t notice the motor much until you need it, then it lets you know it’s there vocally and in its performance. It’s not as far from the S63 AMG’s acceleration numbers either. The reality is that the S500 version is more than quick enough. Real performance is effortless, seemly and sophisticated in its delivery. It can’t be caught off guard and never displays bad manners.

It’s the same in its handling. There are the usual array of comfort and sport driving modes, but it is always best left to its own devices to sort things out. It can be hustled surprisingly quickly for a heavy machine, especially with the way it strings together a series of corners into one seamless surge of silkiness.

It’s an incredibly comfortable cruiser. There is some buffeting with the roof down, though Benz supplies neck-warming air vents and the windscreen uglifying air cap as standard and there’s a wind-blocker that extends and retracts electronically. It’s barely noticeable at urban speeds, but at 130km/h on cruise control it verges on unpleasant. Crossing the country is best done with the roof up, and then it barely loses anything to the coupe for noise levels or comfort. All models can raise or lower the roof in 20 seconds at up to 50km/h.

It’s delightfully designed inside and out, the seats are sumptuous and there are two 12.3-inch TFT screens that double as the instrument cluster and the multimedia screen.

Even if Benz has ignored this market for 45 years, others haven’t. There’s one obvious competitor for the S500 cabriolet, and that’s the Bentley Continental GT, which is more expensive and, maybe, not quite as refined or charming.

Then there’s the S63 version, which is a different animal altogether. It’s not just faster, but it’s more aggressive in its sound, in its vibrations in the cabin and in its ride. Its grip levels from its 19-inch tyres are astonishing in something weighing so much, and it changes direction with an alacrity that has to be experienced to be believed.

It’s more raucous at every step, with bumps crunching into the cabin that just weren’t there in the cheaper car, though it displays stronger brakes and faster reactions at every turn.

While it’s a great accomplishment in engineering, it’s not as complete a car as the S500. It’s as though it’s being pushed into being something it was never conceived for and it can do it, but it’s not a natural at it.

Not that that will stop anybody with their eyes firmly planted on one.