Technology has always been a big part of these cars too. Back in the 50s and 60s that included fuel-injection, disc brakes, air suspension and fully lined convertible roofs for coupe-like refinement when driving with the roof up. And after safety concerns all but killed off the genre it was innovation like pop-up rollover tech on the W124 that enabled Mercedes to once again offer a big, elegant cabriolet and not spoil the lines with ugly roll hoops. Luxury, technology and safety are, again, at the heart of this latest car, up to and including the latest convenience features, driver aids and semi-autonomous driving, this new E-Class Cabriolet bringing this most traditional Mercedes formula bang up to date.
So, we'll accept this isn't a car where sportiness matters as much as it does in some rivals - including the considerably more expensive BMW 6 Series Convertible. But I'm still not sure that that makes a diesel engine an agreeable choice for a convertible, even an exceptionally refined one like the four-cylinder unit in the E220d Cabriolet or the more muscular V6-powered E350d. Each to their own and all that but when it comes to test car allocation my PH instincts have me going straight for the most powerful petrol-powered option - the E400 4Matic with its 333hp twin-turbo V6. Because true wafting requires refinement and reserves of power and torque, even if you aren't wringing the car for every last horsepower.
As you may have heard, this new E-Class Cabriolet is quite a bit bigger than the one it replaces, gaining significant increases in length, wheelbase and width, all carried over from the coupe. This gives it suitable stature over the more junior C-Class equivalent, without treading on the toes of the S-Class flagship. It also helps the looks, the proportions more elegant than before and much nicer than the C-Class. Roof up or down this is one handsome car.
It's nice inside, too. Sit in one of those 60s cabrios and you'll be struck by the sheer extravagance of the wood, chrome and leather trim. And the inspiration for the new car comes from here, not the hard-edged severity of the W124 cabrio.
This is one lavish cabin, especially in my heavily optioned test car with its contrasting black and white leather, broad sweep of aluminium trim and intricate, turbine like air vents. The full width display (the additional screen is an extra £495 over the Comand Online system standard on the six-cylinder cars) is a defiant response to the much-derided tablet style screen of before. The graphics and range of functionality really are dazzling in their scope and quality too. But it does dominate the interior and its sheer size rather conflicts with the voluptuous sweep of the main dash. No pleasing some people, eh?
I could witter on listing all the technologies packed into this car, standard and optional. I'll spare you that - download the brochure if you want the full chapter and verse - but what's satisfying is that for all the Assist this and Magic that it's fundamentally a rather nice car to drive.
In the modern way the twin-turbo V6 is tuned for low-rev torque - the 354lb ft peak weighs in at just 1,600rpm - and although it picks up smoothly a redline in the 6s indicates its comfort zone is in the mid-range. As such it's much better with Comfort selected from the four available Dynamic Select modes, this leaving the nine-speed automatic to slip calmly between its ratios rather than frantically hunt around them as it can when in Sport or Sport+.
The general demeanour feels more relaxed and appropriate to the car in Comfort too, Sport perhaps an acceptable step up to reduce wallow while Individual lets you mix and match your own preferences. Helping that is the sophisticated Air Body Control suspension, multi-chamber air springs meaning both spring rates and damping can be varied according to need. And the ride quality really is exceptional, the system standard on the E350d and E400 and a worthwhile £1,495 option on the four-cylinder cars. The sportier modes are there if you want them but simply seem to send more of the shocks (and the odd shimmy) through the body.
Better to cut back and relax in Comfort mode then. And return to the gadgetry, some of which strays dangerously close to gimmickry. That standard-fit AirCap system for instance. It's intended to reduce turbulence in the interior, especially in the rear. But the roof rail spoiler doesn't look very nice when deployed, adds extra wind noise and when I swapped to the back seat - roomy enough but rather upright - I couldn't tell much difference, even at a steady motorway cruise. And, no, I didn't try this by setting the lane-keeping, radar-monitored cruise control and climbing into the back to let the car chauffeur me autonomously. Though in the right circumstances it will give you long enough hands-free to do so. Possibly. If not to be recommended.
Meanwhile Airscarf - also standard - feels a bit like a dog panting down your neck (again, each to their own) while the £795 Warmth Comfort Package can add seat warmers for the rear and heated armrests up front if you want to enjoy al fresco driving after the sun has gone down. Then there's attention to detail like Magic Vision Control screen washers in the wiper blades that only squirt on the downstroke with the roof down so you don't get sprayed with water. Nice touch.
There's a similar level of detail throughout the car and a sense that the team building it just really love thinking up new ways of using the available technology. Or inventing new stuff. Some of it's worthwhile, some of it isn't. But for all the seriousness there's a sense of fun.
This, then, is a grown-up car. For grown-ups. That doesn't make it a boring one. Far from it, and that combination of maturity and experience is really rather enjoyable to experience. Not to all tastes perhaps. But if, like me, you have a taste for the genre it's nice to see Mercedes going the extra mile.
MERCEDES E400 4MATIC CABRIOLET
Engine: 2,996cc, V6
Transmission: 9G-Tronic automatic, all-wheel drive
Power (hp): 333@5,200-6,000rpm
Torque (lb ft): 354@1,600-4,000rpm
Top speed: 155mph (limited)
Weight: 1,935kg (EU with 75kg driver)
MPG: 34 (combined)
Price: £55,715 ( before options)