Awarehouse in Leighton Buzzard might not be where you’d expect Rolls-Royce to pull the covers off its most audacious and exclusive model to date. Yet if there’s nothing particularly glamorous about the setting in which I’m standing, the open-roof car that’s just been revealed is the very epitome of opulence.

This unique convertible was itself inspired by a one-off design. Unveiled in 2017 at the glamorous Villa d’Este Concorso d’Eleganza in Italy, the Sweptail was built for a Rolls-Royce connoisseur and featured a glass roof and tapered rear end, a design likened to the classic Gurney Nutting Phantom II of the 1930s.

The Sweptail is reported to have cost its owner around £10 million, making it the most expensive new car ever built – until now.

Enter Boat Tail, a coach-built, bespoke Rolls-Royce believed to be making waves around the £20 million mark. To put that in perspective, this gloriously over-the-top statement of wealth is roughly the equivalent of 55 new Phantoms, or 86 Ghosts. Rolls-Royce never admits the exact price of anything, not even a key-fob.

The car, codenamed CB02 until recently, is here in Bedfordshire at a photographic studio, where more than a dozen staff are fussing around in order to create the perfect shot. A burly security chap called Oliver wants me to hand over my phone so I can’t take any duplicitous photographs. “May I sticker your camera?” I’m not going to argue.

The secrecy surrounding this car is extraordinary. I’ve had a tip off about who commissioned the project, but at the risk of upsetting Oliver and the Rolls-Royce legal department, I won’t say much – except that trailing the Cote d’Azur with an eagle eye is probably your best bet of ever catching a glimpse of this stately machine in the wild.

Showing me around is Alex Innes, Head of Coachbuild Design at the Rolls-Royce headquarters in West Sussex. Boat Tail was made under his watchful eye, following several visits from the owner, in a special area within the factory – a section so secretive that only those involved in the project were permitted access.

“Sweptail created a wave of publicity and alerted people to the scope of Rolls-Royce’s ambition to fulfil unique commissions,” says Innes. “It was the catalyst for Boat Tail. I spent a lot of time with the Boat Tail client, soaking up the atmosphere of the incredible world he surrounds himself in, to try and understand how we could characterise that in this new car.” I think I want Alex’s job.

That said, the pressure was certainly on Rolls-Royce to deliver. Instead of guiding a customer through a pre-determined list of options, for Boat Tail, which sits on a chassis of Phantom-like dimensions and is powered by the same 6.75-litre V12 engine, the customer was guiding the designers.

Innis explains that there will be three Boat Tails, all share the same 5.9-metre long body style but have uniquely different interiors, including the contents of the rear-hinged opening sections.

“We made that clear from the start, there will only ever be three built. The owner of this particular car is happy for us to showcase it at an occasion like today but the other two are a little more discreet.

“This owner was heavily involved in the build process at every stage, via the Whispers app (Rolls-Royce’s equivalent of WhatsApp), direct messaging or meetings at the factory. He expected that level of interaction.”

Two years ago, the car I’m looking at now was just sheet aluminium. Six months on, the body panels were still only crude pieces, gently fashioned into shape by hand. “The technique allows larger panels without shut lines, which elevates the car to a work of sculpture,” says Innes.

The hand-painted Azur blue bonnet, which graduates to a softer, lighter blue, is the most eye-catching feature. The iconic, traditional stainless steel Rolls-Royce pantheon grille is also painted for the first time in modern history.

Much of what makes this first Boat Tail so special, however, is hidden from prying eyes. At the rear, twin side-opening compartments are hinged in the middle and open like a butterfly, revealing an Aladdin’s cave of treasures. On one side is a pair of twin champagne coolers, designed to fit the owner’s favourite Armand de Brignac vintages.

Elsewhere, there’s crockery by Christofle of Paris – hopefully dishwasher safe – matched to bespoke salt and pepper grinders, all engraved with the car’s name. Caviar is kept cool in a proper fridge rather than a chiller, with various other food compartments that have been tested in temperatures that range from 80°C to -20°C.

“I enjoyed many meetings with the owner and his wife at their home,” says Innes. “They were wonderfully welcoming. They like to serve food in the mezze style, so we talked about the sense of hosting and grandeur which had to be part of this car. We have road tested everything at 155mph to ensure there are no rattles.”

The Boat Tail’s crowning glory is a parasol that slots into the rear of the car to provide extra shade. With a stainless steel shaft and aluminium coupling, the high-tensile fabric is stretched over carbon-fibre stays. To ensure it will withstand all that the south of France can throw at it, the parasol was tested in Rolls-Royce’s wind tunnel.

In the cabin, the company has worked with Swiss-based House of Bovet to create reversible ‘his and hers’ watches. The centrepiece of the minimalist dashboard is a slot to insert one of the watches, which then becomes the Boat Tail clock. One side of the man’s watch shows the celestial pattern above his birthplace. Beneath the clock slot is a titanium drawer designed to carry another wrist watch, of particular importance in this bespoke Rolls-Royce, Innes explains.

“One of the great characteristics of piloting a Rolls-Royce is the light steering and thin steering wheel. This particular client likes to remove his wristwatch when driving and hated the idea that it would be stowed out of sight.”

I’m told the owner even signed his name underneath the Rolls-Royce motif on the grille before it was mounted, while his wife did the same on the rear badge. They both monogramed the top of the engine too, which might explain why Oliver is there to ensure the bonnet stays firmly shut.

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