If you are looking at these pictures of the Bugatti Veyron 16.4 Grand Sport and seriously considering splashing out the £1m required for the new roadster, a word of advice: wig-wearers need not apply. With the roof removed and the car capable of travelling at 253mph - 371ft per second - there’s little chance of a hairpiece staying in place and even less chance of seeing where it landed in the rear-view mirror.

When Bugatti began planning to lift the roof from the world’s greatest supercar and provide the ultimate alfresco experience, you can bet haircare wasn’t the priority. Getting its engineers to perfect the airflow over the open roof was more pressing.

Now, those on board can lift their diamond-studded sunglasses and see the stars at night. The secret of the car’s appeal is a removable semitransparent roof panel. While it sounds simple, Bugatti’s engineers have had their work cut out ensuring that, with the coupé’s fixed roof removed, the Grand Sport’s body and chassis remain capable of withstanding the twisting forces to which the 987bhp W16 engine subjects them.

Extra measures have been taken to bolster structural rigidity and crash safety. There was never any chance of a fold-down roof: structural and aerodynamic considerations wouldn’t allow it. Instead the roof section, when removed, has to be stowed until you need it, presumably in a safe corner of the garage where nobody will drop a tin of paint on it.

The snappily titled Bugatti Veyron 16.4 Grand Sport is the latest addition to the range (okay, range is a slight exaggeration, as the only variants of the Veyron 16.4 until now have been cosmetic exercises). Bugatti is unhelpfully withholding full information from the public until its debut on Saturday, when about 100 will be offered at a “slight premium” over the coupé (that may be an understatement – we understand the price of the Grand Sport will be deep into six figures).

Built on the same chassis, powertrain and running gear as the coupé, the Grand Sport is capable of matching the coupé’s mind-blowing performance statistics. From standstill, it will fire to 60mph in 2.5sec, a feat aided by the tremendous traction afforded by its four-wheel-drive system. On the way to its 253mph top speed, the roofless wonder can crack 200mph well before a McLaren F1, even with the top off.

It’s enough to leave rivals standing. Neither the 207mph Mercedes-McLaren SLR Roadster nor the 214mph Pagani Zonda Roadster F can compete – although, for the price of the new Veyron, you could buy both and have change left over for any other supercar that took your fancy.

And, as with its coupé cousin, keeping this performance in check is a list of bespoke systems and exotic materials. Michelin spent millions of pounds developing tyres capable of withstanding the temperatures and forces at work at 253mph. A set will cost owners about £12,000 – the same as a new Ford Fusion.

The brakes, developed by AP Racing, are carbon ceramic. The bumpers and some body panels are aluminium. The exhaust is titanium. Magnesium is used in the engine’s cylinder head. And parts of the chassis are made from carbon fibre. It’s like the world’s fastest chemistry set.

Above any of that, it will be the novelty of experiencing the wind in your hair that will have the super-rich adrenaline-lovers clamouring for the Grand Sport. Bugatti says matching the coupé’s performance is only half the challenge; keeping the roof in place, and maintaining stability with it removed, has proved testing, even for a company with the ambition of Bugatti.

The hyper-roadster’s release is timed to coincide with the Pebble Beach Concours d’Elégance in California, where the world’s greatest cars are brought together to compete for the ultimate prize in the glitzy world of classic cars.

After the gongs for best in show have been handed out next Sunday, guests will get the chance to become the first owner of a convertible Veyron at the annual Gooding & Company auction in Pebble Beach. The successful bidder for lot 134 in the sales catalogue will not be able to drive away in a Grand Sport that evening but will become the owner of the first Grand Sport to be built, scheduled for spring next year – just in time for summer. No sign of a crunchy economy here, then.

With a standard Veyron costing about £1m (up from £839,000 last year because of the shifting sterling-to-euro exchange rate), those in the know are predicting that the bidding could reach near double this amount on the night. The winning bid will be donated to charity – after Bugatti has deducted the Grand Sport’s list price. A little uncharitable on Bugatti’s part, perhaps?

Visit the auctioneer’s website at www.goodingco.com for more details. And if you’re the unlucky underbidder on the day, don’t worry: I’m sure Bugatti will make you another one – for a price.

- Daytime-running LEDs have been added to the Grand Sport’s headlights

- Seen with the roof on, as in the photograph bottom left, the Grand Sport closely resembles the original coupé version; once the lid is off, it brings to mind classic Bugattis of the past. The computer rendering shows how the roadster has sacrificed none of the streamlined élan of the hard-top Veyron

- We can’t see any way that the roof panel can be stored in the car so we expect owners to leave it at home and check the weather forecast before setting out

- The W16, quad-turbo engine delivers 987bhp and will propel the Grand Sport roadster to 253mph

- Of the 300 Veyrons that Bugatti said it would build, about 245 have been sold. The dealer that has sold the most is Jack Barclay, part of H R Owen in London

- Structural work had to be done to the car to preserve the strength of the body shell once the roof had been removed

Hot Wheels specs

MODEL Bugatti Veyron 16.4 Grand Sport
ENGINE 7993cc, W16
POWER 987bhp @ 6000rpm
TORQUE 922 lb ft @ 2200rpm
TRANSMISSION Seven-speedDSG with paddle shift
FUEL / CO ACCELERATION 0-62mph: 2.5sec
TOP SPEED 253mph
PRICE £1m approx
ROAD TAX BAND G (£400 for 12 months)
VERDICT The fastest way to lose your head

Harry Metcalfe is editorial director of Evo magazine.

Additional reporting: James Mills