Three men in dark suits peered through the door of the Roller and squinted at the interior roof, which was studded with a thousand pinpricks of light, like stars. Chinese millionaires purchasing bespoke Rolls-Royce Phantoms may choose to replace the normal interior light with these LEDs - or perhaps add a safe in the boot and their own company logo alongside the customary Flying Lady adorning the radiator.
The whole package would set them back the equivalent of £500,000, but there was no shortage of potential buyers among the crowds perusing the Lamborghinis, Bentleys and other luxury models at the Beijing Auto Show this week.
China is now the fastest-expanding car mar- ket in the world, about to overtake Japan and approach the US for top slot in global car sales. The posh and pricey end is growing exponentially, as coal-mine bosses, property speculators and industrialists get wealthy on China's booming economy. Rolls-Royce says that China is its third-largest market after the United States and the UK; Porsche expects to double sales this year.
At the bottom of the scale, the cheapest Chinese-made saloons sell for as little as £2,000, making them accessible to the aspiring middle- class families who crowded into the show, collecting glossy bags of leaflets and CD-Roms with slogans such as "Build Your Dreams" and "Drive to Success". Some were seriously considering buying, while others were just longing.
"If I had a car, my life would be totally different from today. I could move around. I would meet more friends. Everything about my life would expand," sighed one young man, who said he was in the military, staring plaintively at the Cherys, one of China's most successful brands.
"I like Mercedes and BMW the best. But the Audi A4 and the Mazda 6 are more practical," explained a leather-jacketed woman in her early twenties, who said she did not yet have a car.
Not owning a car didn't stop the punters from having opinions. A young woman in a checked coat, with a black beret perched fetchingly on her head, was dismissive.
"I don't have a car, but for an international auto show this is not very impressive," she said. "They only show popular cars. I would like to see more concept cars."
In Beijing, public transport is poor, and plans to extend the underground rail network are moving slowly. (Another plan to build five major motorways underground has not yet been approved - thank goodness.) A thousand new vehicles drive out of showrooms on to the streets of the capital every day, adding to the two and a half million already stuck in traffic jams or moving at less than seven miles per hour - slower than the bicycle for which China used to be famous. Here, as elsewhere, buying a car is a statement of how you want to live, rather than a rational choice.
"The car has taken China by storm," said Jason Li, a Chinese-Australian who consults for the China Automobile Association. "The people who go to the auto show are essentially middle class - those who came out of communism. Now they can afford to buy a car and drive wherever they want to go. It's such a phenomenon, such a symbol of China's economic development, such an expression of freedom for people."
Inside the show, anorexic Russian models with porcelain doll faces lean across the bonnets of Audis and Toyotas, while the punters take pictures with their mobile phone cameras. Young men queue to get in the driver's seat of a computer-simulated Mini, while a woman in shiny black shorts gyrates next to a golden hatchback.
Outside, a dense smog of pollution encases Beijing, forcing planes to remain on the runway and drivers to switch on fog-lamps at noon. On Monday this week, as the car show opened, the air quality index reached 414 - a hazardous level at which the elderly are advised to remain indoors. Since July, every third day Beijing has registered above the level considered acceptable.
In recent years, the authorities have moved industries away from the capital, in an attempt to clean up the atmosphere, but cars are now the main cause of Beijing's poor air quality. Du Shaozhong, deputy head of the Beijing Municipal Environmental Protection Bureau, says the capital's vehicles emit 3,600 tons of pollutants every day.
Several manufacturers were promoting environmentally improved cars at the show. General Motors says its new hybrid 2.4-litre vehicle for the Chinese market has a 20 per cent improved fuel economy. The government has announced a "green auto" certification system, but China's future growth is still primarily based on petrol and diesel-driven vehicles.
On current trends, by 2020 there will be 100 million cars on China's roads. The families at the show were - in the words of its slogan - "Chasing the dream". The problem is that damage to the environment may be so severe, they may destroy the lifestyle they want to create.