Sensational - that's the only word for the 911 Turbo Cabriolet's performance. Porsche's new range-topping convertible offers huge pace in every gear and has a top speed of nearly 200mph, yet is easy to drive at low speeds and live with every day. As it costs £8,340 more than the hard-top, only the wealthiest of buyers will be able to enjoy it. But it oozes engineering quality, and adds yet another string to the 911's bow.

Purist sports car fans don't like the 911 Cabriolet. Believing the drop-top to be a compromised version of a motoring legend, some see it as like chopping the head off the Mona Lisa. But Porsche is ready to change their minds with its brand new open-air flagship - the 911 Turbo Cabriolet.

Sharing the same 480bhp powerplant as its fixed roof brother, the new forced induction range-topper tips the scales at only 42kg - or half an adult passenger - more, and is one of the stiffest convertibles in the world.

Climb behind the wheel, drop the hood and you can immediately get as close to the action as possible, with four-wheel drive making the most of the newcomer's 620Nm of torque. In low gears, the Porsche surges forward with real pace, and without a roof, the sensation of speed is even more pronounced.

Chassis engineers have given the convertible all the agility it needs to take on its most capable competitors. Turn into a corner and the nose darts towards the apex, while the German firm's latest traction and stability programmes help to give all four wheels optimum grip. Only over bumpy surfaces do the windscreen pillars start to flex slightly - but it's never intrusive.

Our sole gripe is that the accompanying scream from the turbochargers isn't particularly pleasant. Where an Aston Martin or a Ferrari offers a spine-tingling engine note that is all the better enjoyed from a convertible cabin, from inside the 911 it sounds as though the turbos are tearing at the air to feed the flat-six unit.

However, nothing can detract from the performance. The six-speed manual car covers 0-62mph in four seconds exactly, but on the race track, it's the thrust available after you have dispatched the benchmark sprint that really sets this new Porsche apart.

Pay extra for the optional Sports Chrono Pack, and you get an overboost function controlled by a Sport button to give an even more brutal shove in the back. On top of that, the aerodynamics allow the 192mph top speed to be reached even with the roof down...

At lower speeds, the standard-fit wind deflector almost completely eradicates buffeting, while the electrically folding soft-top can be opened and closed at up to 31mph.

It's all part of the package that makes the 911 convertible so easy to live with every day, something which is enhanced by the manufacturer's claimed 21.9mpg combined economy - although we were unable to match this figure during our drive. Even the ride quality isn't too harsh at cruising speeds if you disengage Sport mode.

As you would expect, the cabin is superbly finished and ergonomically excellent. Just don't think of the newcomer as a four-seater, because only children will be able to squeeze into the back. It's not only the Cabriolet's performance which is jaw-dropping, though - its £106,180 price will stop most people in their tracks as well. That's £8,340 more than the Turbo coupé, although still £24,645 cheaper than Ferrari's F430 Spider.

What's more, this figure can be inflated all too easily. If the excellent standard steel brakes are not good enough, you can pay £5,800 extra for ceramic discs, while the Sports Chrono pack adds £1,015. Naturally aspirated versions of the 911 Cabriolet represent much better value.

So is this the Porsche convertible that can finally convert the purists? Look beyond the price, and few will be able to question its abilities.