Here's a quote from a 2002 Bentley Arnage Red Label Brochure:
"As you move around the Arnage, reflections from the paintwork promote these details, and create a sense of movement. To achieve the 'mirror' paint finish requires rigorous inspection and preparation. Every motor car is carefully examined in a room bathed in bright light to identify any inconsistencies in the panelwork, before the body is sanded and polished by hand. Then, multiple layers of paint and lacquer are applied in a controlled atmosphere free from dust particles and other airborne impurities, before a final polish that takes up to 10 hours. The paint finish which results is spectacular in its clarity and lack of texture. "
Also mentioned in the Exterior Specifications:
'Mirror finish' paintwork.
Paint range of 27 colours plus personal specification facility.
Flexibilised polymer clearcoat.