Bentley has removed the top from its Arnage to create a hi-tech convertible beneath a profusion of Edwardian style, says Guy Adams

Bentley has a neat way of summing up its position in the luxury-car market. If a Rolls-Royce is something you're driven in, it says, Bentleys are cars that you actually drive. Both brands demonstrate your considerable wealth; only one will also command "respect" from the grubby proletariat.

This thinking underpins the latest addition to its gas-guzzling range. The Azure is classically swanky. It costs £222,500 (including taxes) and oozes burnished wood, chrome, and baby-soft leather. But for all the expensive trimmings, one thing sets it apart from your ordinary plutocrat's saloon: it doesn't have a roof.

From an engineer's perspective, chopping the lid off a normal motor (it's based on the £170,000 Arnage) poses important technical problems. We'll get to those later. To the layman, it's also interesting. If your average Bentley beams from a mock-Tudor driveway in the Home Counties, convertibles make a more exotic statement: less leafy Surrey, more la dolce vita.

So, it's off to Milan for the official launch. The location is Lake Como, holiday home to such style icons as George Clooney, Donatella Versace and, ahem, Luciano Pavarotti. Our residence: la Villa Passalacqua, the former lakeside pile of Vincenzo Bellini, a 19th-century composer who gave his name to the classic Italian cocktail.

Parked on the lawn at sunset, with Signor B's arias tinkling in the background, the Azure makes a splendid style statement. It's a motor for a seriously large home (the front of Passalacqua has 38 windows) in a hot place, the car of choice for people whose pre-dinner Bellinis come ice-cold, from trays held by grinning flunkies.

It's also, quite obviously, a head-turner. The traditional Bentley shape, with a square front end that sticks two fingers up at any need to be streamlined, is reassuringly beefy. Its stainless steel front grille and "flying B" mascot are a throwback to more extravagant days. Twelve-spoke alloys and the "wow" factor of a convertible ice the cake.

Inside, the dashboard has Edwardian elegance: round instrument panels laid into finest walnut; air vents operated by low-tech plungers. The bespoke interior, sourced from well-groomed cattle, seems designed to compliment one of the local silk suits. When your roof comes off, the good people of Como say "buenissimo!"

The key, though, is to have substance with your style. For a quarter of a million quid, you jolly well deserve it. So those vents pump out fully-conditioned air and that uncomplicated dashboard hides Bond-style technology. Sit down, and computerised seats will envelop four well-lunched bottoms. At the push of a button, the hydraulic top retracts as smoothly as a CD from your Bang & Olufsen.

And then, you turn the key in the ignition. The Azure's engine is a rip-snorting piece of kit: 6.75 litres of twin-turbocharged V8 that purrs with the idle menace of a big cat on its post-lunch doze. Slip the (chrome and leather) gear lever, and it crunches up gravel driveways like a hovercraft; put your foot down, and you'll feel the reassuring grunt of 450bhp.

Steering a chariot this big (5.5m long, 2m wide) can be alternately fantastic and exasperating. On narrow, urban roads around the Italian lakes, the Azure's elephantine dimensions make for slow progress. Lorries in the opposite direction threaten expensive scrapes, and prompt minor shrieks from Bentley's PR team. But set foot on the motorway and you're in a different league.

The traditional faults of a convertible - shaky ride, poor handling - stem from the fact that a roof adds essential stiffness to a vehicle's frame. Bentley has combated the problem by adding carbon-fibre cross braces to the chassis and strengthening the front windscreen to such an extent that it could support the weight of not one, but two Azures perched on top of it.

The dividend is a de facto roll bar, and smoothness at high speed. With the three-layer fabric roof up, it's almost silent, even at high speeds. The motor does a fair old lick: 0-60 in 5.9 seconds, 0-100 in 14.4, and a top whack of 168mph.

The Azure's ideal terrain, though, is challenging, power-hungry, country roads. We took the mountain path up to St-Moritz. Here, the double-wishbone suspension, with "computer-controlled adaptive electro-hydraulic damping system", as bigged-up in the owners' manual, allows passengers to relax into a hairpin, even in the back seats.

Crucially, for a convertible, your Azure can also mix it with the sporty set. It has serious muscle. You turn off the traction control, disable ABS, floor the throttle on a bend, and lay down rubber on Switzerland's impeccable roads. Look in the rear-view mirror, and a cloud of tyre smoke fills the Alpine air.

It's traditional here to express reservations. But there aren't many. Serious cash will buy a serious motor, with the performance of a supercar, the excitement of a convertible, and the comfort of the finest luxury saloons. It seems built to last, too. Bentley tests kit by parking it in the Arizona desert for six months and checking that wood, paintwork, and leather stays in shape.

Critics might caution about the practicality of driving the Azure in a city. I'd second that. It's too unwieldy to cut the mustard in, say, London. There's also the pollution issue. Who wants to breathe in smog from behind the wheel, particularly when you are adding to it at a rate of roughly 10 miles to the gallon?

Bentley, though, knows its market. The Azure will sell in handfuls (it reckons roughly 150 a year, across the world, with the lion's share going to the US). The average buyer will already own eight cars, meaning - or so Bentley's logic goes - that Azures will spend less time pumping out CO2 than ordinary motors.

Parked up by Lake Como, watching yet another perfect sunset, I'm almost won round to its way of thinking. Green or not, this is motoring at its most decadent. Now, where did I put that spare quarter of a million?

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