It uses the same parallel hybrid setup as the forthcoming A6 hybrid, with a modified 2.0-litre TFSI engine powering the front wheels and disc-shaped electric motor for the rear, mounted in a crash-proof compartment in the boot. 

The driver can select between five driving modes, including using either of the two power sources independently, or combining them for an output of 242bhp and 354lb.ft. This gives the A8 pace to match conventionally-powered luxury cars, passing 62mph in 7.7 seconds on the way to a top speed of 148mph.

Yet economy is the best in its class. The A8 hybrid returns over 44mpg, with CO2 emissions under 148g/km, and is capable of cruising at up to 62mph on electric power only. Like all of Audi's part-electric vehicles, it's marked out by a set of turbine-style alloy wheels.

Pricing and official consumption figures will be announced closer to the launch.