PLUTOCRATS with long legs will be happy to pay £799 per inch for extra stretching room in the rear of the new Audi A8 L limo as they're whisked from one board meeting to another.

The big Audi saloon is a 13cms stretch (five inches in old money) over the non-L model of A8 - but both cars represent a technical tour de force aimed at some formidable, and also German opposition.

This end of the ultra exec saloon market is dominated by the Mercedes-Benz S-Class but Audi must be hoping fresh looks and a raft of high tech features will tempt wealthy owners to switch from three-pointed star to four interlocked circles.

Priced from £69,100, the new range combines bold looks on the outside - and an emphatically huge radiator grille - with an interior where big blacked out screens make most buttons redundant in an atmosphere so rigorously laid back it might almost be Swedish.

The non-stretched A8 is a big beast at 5,172mm long and the A8 L adds 130mm and £3,995, for which you get the extra rear leg room, heated rear seats, your own air conditioning, electric sunblinds and a remote control that lets you play back seat driver.

Whatever A8 tempts you it will come with quattro all-wheel drive and an eight speed automatic gearbox. There is also the promise that - one day soon and when the legislators can agree - your car will be ready for semi-autonomous driving.

The days of driving yourself in town on the motorway will begin to fade into memories and you'll even be able to put the car into the garage as you stand outside. But not quite yet.

The range debuts with a pair of 3.0 litre V6 engines, a 335bhp petrol and 282bhp diesel and there are larger diesel (4.0 litre, 429bhp) and a flagship petrol (6.0 litres and 12 cylinders but no quoted power yet) on the way.

All four of them are what Audi calls a mild hybrid, which uses stored electrical power to let the car coast with the engine switched off and stay off longer when pulled up at the lights.

It mildly benefits both fuel consumption and tailpipe emissions, with the diesel A8 claiming 50.4mpg and 146g/kms allied to a top speed of 155mph and sprint to 62mph in 5.9 seconds.

Figures for the longer and slightly heavier A8 L are near enough identical and an owner is unlikely to worry about the 33.8mpg recorded on a not very demanding drive at the car's press launch in a £72,210 A8 L diesel.

Of more concern will be how the car drives - and rides - and here the message is mostly encouraging. With air suspension standard in place of the usual steel springs the A8 is always a comfy place to while away the miles.

Show it a piece of smoothly surfaced road (as close to a German autobahn as you can manage) and the car becomes truly limo like, with almost no noise from the tyres and precious little from the engine either.

Soft leather on the seats (electrically adjusted on the front in A8 and rear too in A8 L) gives a suitably luxurious feel, while a driver is faced with beautifully clear virtual instruments and a glass panel that controls everything from audio and sat nav to heating and ventilation with simple finger taps.

It wouldn't be an Audi if there weren't copious temptations on the optional extras list, from 20ins wheels at £4,450, through glass sunroof (£1,750) to a comfort and sound pack at an eye watering £6,350.

You can spend freely on a Mercedes S-Class too, of course, which will give you a car of similar luxury. But it won't look and feel as fresh and there are a lot of them about...