The figures are impressive, no question, but the crucial question, as always with a decapitated version of a driver-focused coupe, is whether the superficial, ethereal appeal of driving with the roof down can outweigh the engineering and dynamic compromises that come with it.

If you're a diehard fan of the 911 it's hard not to answer with an emphatic 'no' simply out of principle, for a convertible panders to those who are more concerned with sunshine and showing off than steering feel and chassis balance. However, when it comes to the 911 Cabrio, it pays not to be too hasty, for if there's a company you can trust to stay true to its engineering principles it's Porsche.

True to form, the 997-generation Cabrio has been developed to retain as much dynamic integrity as possible, thanks to strategic use of high-strength steel to reinforce the body structure, while keeping the overall weight as low as possible. In fact, there's hardly any difference when you compare the weight of the basic 'body in white', the Cabrio's shell weighing just 7kg more than that of the coupe.
Interestingly, while the world embraces folding metal roofs, Porsche stays loyal to canvas, citing low weight, both of the roof itself and the mechanism to raise and lower it, as its reason for doing so.

With a hard panel above the driver and passenger (which forms the 'tonneau' when the top's dropped) the roof has a taut, snug-fitting look when in place. There's negligible wind noise with the roof up, while a heated glass rear window makes it a practical, all-year, all-weather proposition. Its only weakness, then, is its vulnerability to the vandal's blade.

Dropping the roof is an effortless, one-touch operation, the canvas Z-frame structure stowing neatly behind the seats quickly and tidily. Roof down it looks clean and cohesive, the tail in particular looking less bulbous than the previous generation drop-top. Sadly the coupe's classic profile is sacrificed when the roof is raised, but it remains a handsome car.

Once on the move, with the side windows and anti-buffet mesh screen raised, there's little in the way of turbulence in the cockpit, until you get up to motorway speeds, at which point you begin to feel a gentle wash of air around your neck and shoulders. Even at genuinely high speeds (we saw 120mph or so at times) you remain impressively isolated from the worst of the slipstream.

Dynamically the Cabrio is a virtual facsimile of its steel-roofed relative. You get the same weighty, square-shouldered feel through the steering, the same muscular damping and smooth, linear power. Broken surfaces send the faintest shiver through the structure, but you'd have to have the sensitivity of a scientific instrument to detect any appreciable deterioration in the car's turn-in response or steering feel. As with the coupe, though, that means a helm that isn't quite as talkative or detailed as you might expect of a 911, and a general level of ability that can make rapid progress feel a little too imperious at times, especially when running on 19in rims. No matter how hard you try to unsettle it, it's an unrelenting grip-fest.

As with the coupe, PASM is an option, here calibrated to the specific needs of the Cabrio. From experience in the coupe we've got mixed views on Porsche's Active Suspension Management, feeling the conventional set-up shades it for involvement, but I suspect the more sophisticated control of the PASM system makes more sense in the Cabrio, as it manages to soften the edges of the kind of ridges, potholes and coarse surfaces that would challenge even the most sturdy chassis structure.

A peerless exercise in surgical decapitation, the 997 Cabrio is sure to be a huge seller. Despite the apparent conflict with the revitalised Boxster, it is a different, more vivid experience. And while the core appeal of an open-top 911 might be lost on some of us, if you're a fan of open-top performance cars, Porsche again defines the breed.