The A8 has topped Audi's range - new EV alternatives notwithstanding - since the mid-90s, and now the manufacturer has facelifted the fourth-generation model. Two bodystyles are available, the standard A8 and the long-wheelbase A8 L. We tested the latter, nominally in the entry-level Sport equipment grade, though our test car was a non-standard spec also loaded with option packs. 

The A8 can be had with mild hybrid petrol and diesel engines (or a V8 with the S8 performance model), but the obvious fleet choice is the plug-in hybrid, which pairs a V6 petrol engine with an electric motor. With a total of 462hp, on tap acceleration is hugely impressive for a car this large, however it never feels frantic or rushed - composure is always maintained. Refinement is excellent too, predictably so when running on the electric motor alone. But even when the petrol engine is required it runs very smoothly, meaning the relaxed ambience is maintained.

As we all know by now it's vital to charge PHEVs regularly to get the full economy benefit, and with a car as big and heavy as the A8 L - 5.3m long and well over two tonnes - this will only be exaggerated. That being said, while it will obviously be most frugal on EV-only short trips, on a 110-mile drive starting with a full 17.8kWh battery we achieved over 45mpg according to the on-board computer - a pretty decent figure. While even the 37mpg we recorded on the way back with the battery empty didn't seem too bad. The EV-only range is up to 37 miles in official testing.

Should the person in the back be running late for a meeting, the A8 can corner at speeds that would be beyond many smaller and lighter cars without feeling even slightly ruffled. There's immense Quattro all-wheel drive grip and extremely capable air suspension that holds everything together in the bends without ever compromising the excellent ride quality. Despite its size, the A8 also never feels intimidating or unwieldy to place on the road, while a plethora of sensors and cameras can be specced to help you navigate tighter car parks (including Audi's video game-style virtual display).

Speaking of visibility, top-spec A8s come with fantastic digital matrix headlights. These create essentially a giant curtain of light in front of the car, while strategically avoiding the spots where other vehicles are, therefore providing the best illumination we've seen without dazzling other traffic. 

As befits a car you'd imagine will mostly be chauffeur driven, the best place to appreciate the A8's interior probably isn't the driver's seat. It's very nice up-front, but there's not too much we haven't seen done similarly on other Audis, such as the central double touchscreen set-up. It looks good but features haptic feedback, which can take a bit of getting used to if you are not used to the technology from an iPhone or similar device. On top-spec models the front seats do at least benefit from a highly comprehensive massaging function to help on long journeys.

In the back, especially with the long-wheelbase version we tested, legroom is vast, and speccing the Rear Comfort Pack allows a huge range of electronic seat adjustment. The pack also brings HD rear screens, which can access Netflix streaming and display video content from paired devices, meaning passengers should be well entertained as well as comfortable. Separate rear touchscreen controls operate features such as the audio system, climate control, and sunroof.

One negative note for practicality, at 370 litres the boot seems a bit poky for a luxury saloon, with the PHEV battery taking up space beneath the floor.