Second Rolls Royce Drop Tail is a celebration of gemstones

The removable roof panel is also carbonfibre, which makes it easier for the driver to remove and replace it. It also features a large section of electrochromic glass, which, in the Amethyst, has a subtle purple tint when deactivated and, when switched on, is translucent with a brown hue to match the interior leather.

Aerodynamics played an important role in shaping the Drop Tail. Rolls-Royce said the car’s swooping rear end is “not ordinarily conducive to producing downforce”, which is to say the car was deemed insufficiently stable at high speeds without additional assistance.

Rather than mount a spoiler, the firm tweaked the design of the rear deck to produce the necessary downforce without compromising the aesthetics – a process that took two years and 20 iterations.

The Amethyst’s deck, according to Rolls-Royce, is “the most extensive wooden surface area in [the brand’s] history”. It is finished in Calamander Light open-pore wood trim, which matches the tone of the car’s secondary brown leather – an effect that apparently took six months to achieve. This was done using a completely new veneering process to make it look like one continuous piece of wood.

Each component in the car was stress-tested over 8000 hours at temperatures ranging from 80deg C to -30deg C.

All Drop Tails draw power from the familiar twin-turbocharged 6.75-litre V12 in a bespoke state of tune that boosts power by 30bhp over the Phantom but which cuts torque by 44lb ft, giving total outputs of 593bhp and 620lb ft. Rolls-Royce has not revealed any performance figures, but no doubt the Drop Tail will be a close match for the V12-engined Dawn, with a sub-5.0sec 0-62mph time and a top speed capped at 155mph.

Rolls-Royce design director Anders Warming told Autocar the V12 was used rather than an electric powertrain because the marque is “celebrating” the roadster “and the V12 is a powertrain we will be celebrating for the next couple of years”. Asked when the firm will be ready to launch an electric coachbuilt special based on the Spectre, he said: “Time will tell.”

At 5.3m long and 2.0m wide, the Drop Tail is smaller than the Spectre, with its completely bespoke silhouette defined by a low coupé-like roofline inspired by ‘chop-top’ hot rods.

Inside, the brief was to create an “intimate” environment, with woven leather floor mats and switchgear that is obscured where possible. Only three buttons are left in open view, and they are topped by gems in the Amethyst edition at the request of the customer. On all cars, the powered centre console can be moved to cover the infotainment control dial.

A vast wooden panel cocoons the seats, intended to reinforce the “romantic” atmosphere. It was built by a single craftsman – a former Rolls-Royce apprentice – who is said to have worked on the panel over nine months, in silence, for no more than one hour per day, to ensure complete focus on the task.

This was the “most complicated, involved and prohibitive work of craft ever produced” at its Goodwood factory, said Coachbuild design boss Alex Innes.

The La Rose Noire commission comes with a bespoke watch from Audemars Piguet which also functions as the car’s clock, mounted to the dashboard using a clasp mechanism. The Amethyst swaps this for a timepiece specified by the customer from Vacheron Constantin. It’s handmade in Geneva and called ‘Les Cabinotiers Armillary Tourbillon’, and it has been designed to match the interior colour.

Both timepieces posed a significant challenge, said Innes: “They had to be crash tested, both physically and in virtual simulations, to ensure that the timepiece would remain in situ were the car to experience any sort of abstract movements in a crash situation. [We went to] lengths that nobody would normally go to, were they not instigated by the specific wishes of a commissioning client.”

La Rose Noire was commissioned by a husband and wife who are the heads of a “prominent international family”. It is inspired by their relationship, with ‘True Love Red’ paint paired with a darker shade dubbed ‘Mystery’.