The Lamborghini Aventador LP 700-4v roadster is the most extraordinary car in the company’s illustrious 50-year history, or so said the firm's charismatic chairman, Stephan Winkelmann, at the car’s launch in Miami.

It’s a bold claim, given what’s been served up previously by the famous old supercar maker from Sant'Agata  – the Miura SV and pretty much any version of the Countach are surely contenders.

Then again, one look at the mighty Aventador roadster in the flesh tells you that it is indeed right up there with Lamborghini’s most outrageous creations. It looks like the sort of car Batman might drive on his day off, maybe when he’s on holiday in Miami Beach.

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Don’t for one moment think of the roadster as some kind of folly, however, or as a car that hasn’t somehow been engineered thoroughly for the job. Unlike the Murciélago roadster, which was something of an afterthought to be honest, the open-top Aventador is a standalone model in its own right.

Its styling is unique, considerable care and attention having been employed to ensure it of a separate, more extrovert personality compared with the coupé. And beneath its reptilian-like skin, while it shares its basic carbonfibre tub platform, 6.5-litre V12 engine and seven-speed single-clutch gearbox with the coupé, dynamically it is perhaps more impressive than the fixed head, for reasons we’ll come to in a moment.

Despite weighing some 50kg more than the coupé, Lamborghini claims the Roadster can set exactly the same time around the number one handling circuit at the Nardo test facility in the hands of all its test drivers.

Had the roof simply been removed and various areas of the car not been redesigned to accommodate the one quarter decrease in stiffness, there is no way the Roadster could achieve such basic speed across the ground.

On the road that’s exactly how it feels: pure, fast and sharp, and perhaps even a touch more precise than the coupé at the front end thanks to the fitment of bigger diameter tyres (optional 21-inch 355/25s at the back with 20-inch 255/35s at the front on the one we tested). These, say Lambo’s testers, make a small but key difference to front-end bite during the turn-in phase.

The result is a car that's less prone to understeer in slow corners (which is welcome) without there being any extra nervousness at the back in fast corners (ditto). Overall the Roadster just feels like it has more grip than the coupé everywhere, basically, and at least as well balanced near its monumental limits.

So although it might weigh an extra 50kg, the roadster gives little if anything away to the coupé from behind the wheel. Other than the fact there’s no roof, it even feels the same when you’re in the driving seat, which is no surprise given that the dashboard, instruments, switchgear and seats are all identical to those of the fixed head.

The roof itself comes in two forged carbonfibre panels that are removed by unlocking a couple of latches and lifting them out manually. Each panel weighs just 3kg and stores neatly beneath the bonnet in the boot. Once in situ they render the luggage capacity all but useless, but then, as Lamborghini says, “You don’t buy a car like this to go shopping with”. Which is fair enough, even if it would be handy to be able to put something slightly larger than a toothbrush in the boot when the sun comes out.

Rather more impressive (and entirely believable) is Lamborghini’s claim that the roadster can reach its astonishing 217mph top speed with or without the roof in place. The highest speed I reached was about 160mph along the main straight at the Homestead-Miami Speedway, at which point any noise being generated by the wind was drowned out completely by the machinations of that monster V12.

At lower speeds, however, it’s clear that Lamborghini's designers and aerodynamicists have done a fine job of managing the flow of air away from the cockpit: at 80mph with the windows up and the small rear bulkhead screen raised, conversation is remarkably easy to maintain.

Unlike the Murciélago roadster, there’s a genuine level of refinement to this car’s demeanour when you’re driving it al fresco, up to and beyond three figures.

But the best mode to drive it in is with the roof up and the bulkhead panel that sits behind your head down. This tiny glass panel is the only thing that separates your ears and brain from the screaming, 691bhp V12, and when you lower it the volume levels become cataclysmic.

You can almost smell the unleaded being burned, and it sounds far, far angrier – and louder – than the coupé does at any point within the 8500rpm rev range. You sometimes wonder if your ears might actually be getting damaged.

The 1625kg Lamborghini can sprint from 0-62mph in just 3.0sec, thanks to the traction on offer from its four-wheel drive system and the almighty 691bhp and 507lb ft the V12 offers up. Lamborghini even claims a relatively acceptable 17.5mpg average for it, although emissions of 370g/km of CO2 won't win you any favours when it comes to road tax.

Faults? The ride is skateboard stiff on the public road and the steering weights up too quickly and too much in quick corners. And despite the excellence of the transformation from coupé to roadster, the Aventador still feels like a big, heavy, almost clumsy machine if and when you start to throw it around. But fundamentally it is what it is, and you’ll either love it or hate it for that.

Times may be hard for mainstream car manufacturers at the moment, but for the likes of Lamborghini the opposite is true in 2013, and it’s the Asian market that’s keeping trade strong. Hence the reason why, even at £288,840, the roadster is sold out until mid-way through next year.

It is indeed a crazy kind of world in which a nigh-on £300,000 Roadster can outsell Lotus’s entire range of cars in one year by a factor of three. But then the Aventador roadster is a crazy kind of car. Despite it being one of the more gruesome examples of how the chasm between the haves and the have-nots continues to widen, it’s also a wondrous machine in its own right.

This is a flawed diamond of a car that does things in its own inimitable way, and forget what the rest of us might think in the process. A proper way to celebrate your 50th birthday, in other words.

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