We reckon you’re best off with the entry-level 2.8 V6 – it’s plenty fast enough for most people, as well as providing surprisingly good fuel economy and low emissions. The other petrol engines - a 3.2 V6, 4.2 V8, 5.2 V10 and 6.0 W12 - range from fast to downright ferocious, but running them will cost a bomb. The diesels are tempting, too, with a choice of a 3.0 V6 and a 4.2 V8, both of which provide very strong performance.

All A8s ride on an air-suspension system with four settings. Body control is good for a big car, and the A8 handles tidily for its size. Speed-sensitive power steering makes the A8 easy to drive in town, but it lacks feel at higher speeds.

All of the engines are muted in everyday driving and they issue only a subdued growl under hard acceleration. Road noise is also kept to a low level over most surfaces, while minimal wind noise at speed is only noticeable because of the absence of any other noises.

Prices undercut those of its key BMW and Mercedes rivals, but the A8 isn’t cheap. The diesels retain their value best, but average residual values of around 28% after three years aren’t quite up to those of the S-Class. Most of the petrol engines (the 2.8 V6 aside) give poor fuel economy, although the diesels are better. Every model attracts high company car tax ratings and sits in a high insurance group.

The A8's excellent build quality is one of its major attractions. Throughout the cabin there’s a rock-solid feel, and the gorgeous materials give a real feeling of class. All the engines are tried and tested units, so they should prove trouble-free. However, Audi’s overall performances in our recent reliability surveys haven’t been quite what they should be.

The A8 comes with all the safety equipment you would expect. Anti-lock brakes with electronic distribution of stopping power and a stability control system aim to prevent accidents before they happen. Also fitted as standard are eight airbags, and front seat head restraints that automatically move to counteract whiplash in a rear impact. Security kit is comprehensive, too.

A good driving position and electric adjustment for the seat and steering wheel make it easy to get comfortable up front, while the main controls and instruments are easily reached. A single knob between the front seats controls the stereo, satellite-navigation system and suspension settings, with menus viewed on a dash-top screen, but the system isn’t entirely intuitive.

The A8 has vast cabin space, especially in the long-wheelbase model. Head- and legroom for occupants is superb, and the seats are comfortable and supportive. The boot, likewise, is deep, long and well shaped.

Kit fitted as standard includes climate control, leather trim, electric seat controls, front and rear acoustic parking assist, a CD changer, alloy wheels and adaptive air suspension. Sat-nav, keyless ignition and voice controls are also standard. Sport spec adds sportier suspension and trim.