While their larger siblings in the luxury saloon sector offered acres of space for rear seat passengers, the premium executive saloons were rather mean in this respect.

Cynics might suggest it was a way of guaranteeing sales of larger cars including the A8, BMW 7-series, Mercedes-Benz S-class or Jaguar XJ. It was almost set in stone that if you wanted a classy car that was truly spacious, you had to look to semi-premium and volume executive saloons such as the Volvo S80, Peugeot 607, Renault Vel Satis and Vauxhall Omega.

All this could be about to change, however, with the launch of the new A6. Staking its claim as the roomiest premium executive saloon, it is bound to influence the size of future models from its key rivals, and the fact that BMW, Mercedes-Benz and Jaguar will take notice is testament to how far Audi has travelled up the premium ladder over the past 20 years.

The recent trend of private buyers and user-choosers selecting premium cars is shown in Audi's recent increases in sales in the UK.

From just over 40,000 units in 1999, more than 70,000 Audis found homes in the UK last year and in April 2004 it sold more cars than BMW, Mercedes-Benz, Jaguar, Volvo or Saab.

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Audi's conscious effort to make the new A6 the largest car in its class and the adoption of the new 'trapezoidal' grille design should help those sales continue in the ascendancy.

By the time the launch programme is rolled out (with a new A6 Avant arriving early next year), Audi believes it will have the widest choice of vehicles in the executive sector, with four-cylinder petrol and diesel engines, front-wheel drive or four-wheel drive, six-speed manual, six-speed auto and Multitronic CVT with seven pre-set 'gears' for manual mode.

Audi's FSI direct injection petrol technology makes its A6 debut in the new model with a new 3.2 litre boasting more than 250bhp, with a new 3.0-litre common rail V6 diesel also offering a class-leading power output.

The engines will be joined at launch by a new 175bhp 2.4-litre and a 331bhp 4.2 V8. Two diesel engines will follow later in the year.

A 138bhp 2.0 TDI will arrive in September, and this unit is expected to take the lion's share of A6 sales, while a 175bhp 2.7-litre V6 TDI will be introduced in December. All engines – petrol and diesel – are Euro IV compliant from launch.

The new A6 has the MMI (Multi-Media Interface) by which various auxiliary functions can be selected, adjusted and controlled at a single point behind the gearstick, technology first seen in the Audi A8.

There are three versions of MMI in the A6 with varying levels of features included. MMI Basic Plus is standard on all models.

All cars have an electronic parking brake with a switch instead of the usual lever, meaning there is more space and less clutter next to the driver. Luggage volume is increased to 546 litres – more than any of its rivals.

Also standard across the range are light sensors and rain sensors for automatic activation of headlamps and windscreen wipers. Adaptive cruise control and air suspension are in the pipeline as options during 2005.

The A6 is much larger in every dimension than its predecessor, and the wheelbase has been increased by 83mm for better interior comfort, although not all of the increase is enjoyed by rear seat passengers.

The front suspension has been moved forward for better weight distribution and both front and rear tracks are wider for better driving dynamics.

For the remainder of this year, Audi expects to sell 4,500 new A6 models – the majority to corporate customers – with 2,500 units of the existing A6 Avant.

In 2005, with the new Avant introduced early next year and most engine variants in place, the total is expected to reach 15,000 units: half saloon, half Avant.

Behind the wheel

LIKE the outgoing A6, the new model is understated and elegant. But the new-look grille and larger dimensions means it has more presence on the road. The new A6 will turn heads, but you also get the feeling that it knows it's being looked at.

There is an air of confidence about the car which begins with the bold grille and elegant proportions, and continues inside. The centre console is angled towards the driver and the steering wheel centre echoes the shape of the grille.

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Audi has become famous in recent years as a benchmark for interior build quality. The new A6 is no exception, with paper-thin gaps between the sides of the dashboard and the closed front doors.

Its clean design is almost taken to extremes – the glove compartment door is uncluttered and is opened by pushing a button alongside the MMI screen on the dashboard, which then activates an electronic release.

The 3.0 TDI is only available with quattro four-wheel drive and initially only with a six-speed Tiptronic automatic, hence its mediocre fuel consumption figure of 33.2mpg on the combined cycle.

However, the engine could turn out to be the pick of the range so far, with more torque on offer than the 4.2 V8 and reaching its maximum of 331lb-ft at a remarkably low 1,400rpm, keeping it there until 3,250rpm. Being available at such low revs more than makes up for it being behind the BMW 530d and Mercedes E320 CDI, which offer a maximum of 369lb-ft.

With the automatic transmission the throttle response is almost instantaneous – perhaps a momentary lapse as the engine decides whether it even needs to kick down – and the whole process of overtaking becomes kerfuffle-free.

Surroundings blur as the 3.0 TDI relentlessly picks up speed and the engine note comes alive and sounds rather sporty too. The diesel is always quiet – almost inaudible at low revs – and when warm is also surprisingly quiet from the outside.

Brakes are supremely effective, although they can feel a bit snatchy until you get used to them. Their stopping power is beyond question as they hauled the car to an emergency stop on our test route in very short order.

Otherwise the new model rides better than the outgoing car – still firm but much more forgiving over sudden bumps – and the A6 was unflustered by our twisty test route with sharp hairpins and sudden changes of direction.

Rear legroom is generous, and three average-size adults should have no trouble filling the rear bench. When I tried it with two colleagues with broader shoulders than myself, it was rather tight, despite the car's extra width.

The petrol-powered 3.2 V6 FSI majors on fuel economy and refinement. With the manual transmission fitted it records the same fuel consumption and CO2 emissions figures as the 177bhp 2.4 V6.

The six-speed manual gearbox makes the car feel more responsive than the auto (with quattro fitted) and has a light gear change action, but the throw is too long to make it genuinely sporty.

While Audi claims its speed-sensitive Servotronic steering helps give the car a sporty drive while making it more manageable at parking speeds, I found it too light on twisty roads at high speeds. It was as precise as could be, but there was nothing reporting back on what the front wheels were doing.

Audi claims it offers greater feedback at higher speeds, so presumably I wasn't driving fast enough.

Driving fast comes easy to the 4.2 V8, which offers the liveliest performance in the range from launch and comes with a muscle car engine note. When driving the V6 models, you come to the conclusion that their level of performance would be more than adequate for most people's needs, but the V8 soundtrack and brutal acceleration become much more appealing when experienced first hand.

Verdict
The new A6 is a strong proposition from Audi in the highly competitive executive car sector. The range of cars at launch point to a potential E-class beater, but the full picture will be unclear until the rest of the range appears later in the year.