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Click for pictures“Beauty and the Beast.
  We’re not talking fairy
tales here. Get behind
  the wheel of Audi’s
  potent twin-turboed V8
  diesel and you’ll find
  both live happily ever
  after in the latest A8”

IF YOU'VE NO IDEA what Audi's 'Vorsprung durch Technik' catchphrase actually means, don't worry. Because all you really need to know about Audi's flagship A8 range is that it's about having your cake and eating it. And today you simply cannot mention the respected German Mercedes and BMW in the same breath without including the equally highly-rated Audi marque.

A8 customers can now select from a 10-model range that starts with
a 3.2-litre V6 costing 47,930 and tops out with the 77,360 6.0-litre W12. However, it's in between the entry-level and range-topper that it gets really interesting. Because that's where you'll find the A8 4.2-litre TDI quattro, road-tested here. While its list price is 58,420, our test car was fitted with a number of optional extras that bumped the price up to 71,400.

A sizeable sum of money, you'd be right in thinking. And, as a potential buyer, your next question would doubtless be: "So what do I get for my money?" The answer: A lot. For a start, the A8 is a limousine that doesn't just think it's a sports saloon — it is a sports saloon. What makes the A8 so appealing is that you can place the emphasis equally on both definitions. And not be disappointed.

Externally, the thing you notice before all else is Audi's new styling signature — the large single frame front grille. And it looks absolutely right fronting the big A8's nose. At the back, there are two large-diameter chromed tailpipes that hint at the power while coyly pointing down at the tarmac. Along with the new grille comes a comprehensive package of upgrades, not least of which is the 322bhp twin-turbo-charged 4.2-litre V8 diesel engine. Its predecessor, the widely-acclaimed 4.0-litre TDI introduced in 2003, quickly made the A8 the best-selling V8 luxury diesel saloon with a 71 per cent market share.
A hard act to follow.

This new 4.2 doesn't just follow — it leapfrogs ahead. Not just a slightly larger capacity version of the original engine, it's an entirely new V8 TDI in its own right. And an important facet of its new design is its weight: a low 255 kilograms and a useful 15kg lighter than the
4.0 TDI, which makes it one of the lightest V8 diesels ever produced.

Audi has a knack of making exceedingly handsome cars. Even the A8, the biggest in their range, manages to look dapper despite its size.
And Big, in this case, is with all the benefits and none of the penalties thanks to the A8's all-aluminium construction. About the only visual clue to its size are the sleek five-arm design wheels. At a casual glance, they look to be of an average size compared to the bodywork dimensions. But walk up close and check and they turn out to be
19-inch by nine inches wide. Only when you see this Audi parked alongside other cars do you realise just how big the A8 actually is.

The good news is that it's big on the inside too. Cabin ambience is an attractive mix of form and function, sporting feel and luxury. Many people would agree that Audi interiors are some of the very best around. Both powered front seats have a four-setting memory and, in addition to being resoundingly comfortable and supportive, they offer an amazingly comprehensive range of adjustment over and above all the usual fore/aft, up/down movements with powered headrest and seatbelt height, extending thigh support and up/down/in/out electric lumbar support.

The driver also enjoys electric height/reach adjustment of the steering column and an easy-entry/exit facility, along with a multi-function
4-spoke Sports wheel wrapped in extremely grippy yet very smooth leather. Most notable, the backrest also adjusts in two sections at the touch of a switch, making the perfect driving position possible. The
6-setting heated seats are superb. You're so comfortable, in fact, that you never for one moment think to ask yourself if you are. Which says it all.

Space there is aplenty, both front and rear, for storage as well as people. And the cavernous and intrusion-free boot is big enough to sleep in — should you ever wish to do so! The light and airy rear cabin ensures back seat passengers travel in first class comfort with their own dedicated climate controls, powered side and rear blinds and a Bose surround sound system. No skimping with the electric windows either as all four feature full one-shot up/down operation.

The top class build quality and materials that have become a byword for Audi products can assuredly be taken for granted in the A8. In addition to being beautifully built, the interior is also elegantly and ergonomically laid out. Positioned comfortably in the centre console behind the selector gate, Audi's foolproof Multi Media Interface neatly and seamlessly integrates a whole range of essential car/driver functions encompassing entertainment and driver information into one easy-to-use system. Amazingly intuitive and simple to learn, it's the best of its kind on the market.

As with nearly everything about this A8, there's something to like in addition to each particular item or feature itself. Take the MMI's 7-inch LCD colour screen. It folds out of the centre of the fascia with a flourish, to sit perfectly in your field of view. Should you wish, it will disappear back as magically at the nudge of a button. Even the cool feel and engineered action of the smoothly polished aluminium electro-mechanical pull-push parking brake switch located on the centre console, makes you want to release it manually with a quick pull upwards — despite the fact that it does so automatically as you drive away. Wherever you look in the cabin, it's hard not to feel good about what you see.

And while the driver only needs to apply fingertip pressure to work it, the parking brake is designed to cope with gradients of up to 30 per cent. Exceed this and a warning will flash up on the driver's display screen between the deeply recessed rev-counter and speedometer. And, again taking things that one step further, the parking brake makes it easier to pull away without jolts or rolling backwards on inclines by way of an integral starting assist function. And talking of parking, in spite of its size the A8 is easy to manouevre into parking spots thanks to a its good turning circle and the superb parking sensors that provide a clear schematic of the car along with any obstacles around it on the MMI screen.

Everybody knows that diesel is the prodigal son of fuels. Modern day state-of-the-art diesel technology has addressed all of the earlier shortcomings to the point where more and more luxury and executive cars are fitting magnificently powerful diesel engines to their flagship models. And more and more customers are demanding them. Hardly surprising, given how refined this 4.2 TDI unit is.

The TDI V8 in this Audi really has to be heard to be believed. Or rather, it doesn't. Inside or out, there really are no audible clues that fitted in the engine bay is an oil-burning engine. In addition to twin turbo-chargers (one serving each bank of four cylinders) and intercoolers, Audi's new 4.2-litre V8 features the latest-generation common rail system along with state-of-the-art piezo injection. You don't have to understand the technology to appreciate it. Suffice to say this is one ultra-smooth V8.

Hardly a month goes by without someone, somewhere singing the praises of yet another new diesel that's 'impossible' to tell apart from
a petrol unit. Unfortunately, many diesels are still identifiable as such. However, when we say that Audi's 4.2 TDI is — whatever the driving conditions and driving style — virtually impossible to tell apart from a V8 petrol engine, it's not just hyperbole.

And that's just the beginning. Currently the world's most powerful production diesel engine, the TDI is quicker and has more pulling power than just about any equivalent capacity petrol unit. The secret of the TDI's substantial mid-range acceleration is that its maximum 480lb ft of torque is available from 1,600 to 3,500rpm. At any speed, and on any road, this fabulously brawny twin-turboed V8 diesel engine is never short of enormous and immediate thrust. At the UK's legal limit the V8 TDI's crank is turning at a lazily unstressed 1,650rpm.

The six-speed Tiptronic auto always manages to be in the right gear at the right time and it shifts creamily up or down the ratios. Raw figures can't do justice to the manner in which this big car piles on the speed. Zero to 62mph takes just 5.9 seconds. Overtaking has rarely been so enjoyable.

The V8 TDI's top speed is electronically limited to 155mph but it rockets off the line with perfect traction — thanks to its standard-fit quattro four-wheel drive — in just 5.9 seconds. Astonishingly, it will return 30mpg on the combined cycle. Think that's good? Then how about 39.2mpg cruising the motorways — where, incidentally, it feels utterly composed. Even the real-world town figure is remarkable for such power and performance: 21.2mpg. For the record, we averaged 29.1mpg over mixed driving conditions during our 400-mile, week-long road test.

We've driven a number of A8s in our time and the thing that never ceases to amaze with each fresh re-acquaintance is how they seem to shrink their dimensions once you've driven those first few 'getting-to-know-you' miles. Out on the road the A8 TDI's capable chassis exhibits an agility that contradicts everything you're expecting given its size, surprising you with the accuracy with which it can be piloted through tight gaps.

This big car can really ride and handle, especially in Sport mode. The harder you push, the more poised the A8 feels. This is partly down to its stiff aluminium bodyshell which provides a perfect platform for the finely resolved fully-adaptive air suspension system (it uses a four-link front and trapezoidal-link rear geometry set-up). The driver can select any one of four suspension settings that each have their own distinct ride height and damping characteristics and which are continuously controlled and adjusted in real time.

These range from Automatic through sporty, lower-riding Dynamic to the serene Comfort setting. Below 50mph there's a Lift mode for extra ground clearance when driving over uneven terrain. A click of a switch via the MMI's 'Car' menu is all it takes to switch from near magic-carpet suppleness to taut, roll-free handling. Adding a massively reassuring layer of competence in the background is Audi's quattro permanent all-wheel drive — still a unique feature in the luxury class and providing outstanding traction and control in all conditions.

The six-speed Tiptronic comes 'bundled' with a Dynamic Shift Program and a Sport program. The DSP avoids excessively frequent gear changes and this is especially noticeable when the performance of the V8 TDI is being fully exploited. When Sport mode is engaged, upshifts are prevented if the accelerator is released suddenly.

If the ESP's lateral acceleration sensor then detects that the A8 is cornering, upshifts are blocked until you are through the bend. This avoids the 'change happy' problems that blight some conventional automatic transmissions, making an inappropriate upward change on entering a bend followed by a downward change coming out of it again.

Should you choose to, you can flick the selector sideways to engage sequential manual shifting. Upshifts are made by a short, firm push forwards and downshifts by a light pull backwards on the selector lever. The lever's action has a clear-cut action and 'feels' directly connected to the gearbox. Manual or automatic, the gear engaged is always clearly displayed in the instrument panel.

Refinement is exceedingly good. Cruising effortlessly at speed, the lusty V8 is near silent. Deceptively so: Guess what speed you're doing. Then double the figure you first thought of. Flick a glance at the 170mph speedometer and I guarantee you'll be shocked. As a policeman once said to a friend of ours: "Excuse me, Sir — are you having trouble taking off?"

Wind noise is virtually non-existent — barely a flutter. And despite the huge 19-inch alloys shod with 255/40 Bridgestone tyres, there's no discernible road noise either. All of which makes it easy to forget that this limousine-sized A8 can be just as nonplussed ducking and diving as it is promenading. Want to see? Stamp on the accelerator pedal — better still, slot it into Sport mode first for some real fireworks. You'll be rewarded with an emotive, bassy V8 growl that reminds you that within the A8's beauty lives a mighty beast.

Another key component of the A8's composed and supple handling is
its rack-and-pinion steering with servotronic variable ratio and speed-dependent power assistance. In practice it's nicely weighted, accurate and feeds the driver enough information to fully exploit the A8's sporty handling abilities. The brakes, too, are nicely judged: strong, with substantial belt-tightening retardation when you push down hard on the pedal. And so they should be with enormous 360mm discs at the front and 310mm at the rear. They're also easy to modulate, which helps keep progress smooth when you need to really press on.

Safety obviously begins with the quattro permanent four-wheel drive system. It continues with active front head restraints, double-glazed tinted glass, two-stage airbags with pre-tensioners for the driver and front passenger, ABS with electronic brake-force distribution, Traction Control and an Electronic Stability Programme, side airbags for the four outer seats, side-impact protection in all doors and Audi's Sideguard airbag head-protection system.

Brilliant Xenon headlights — both main and dipped — provide a safe spread of non-dazzling light from dusk to dawn and are undoubtedly an important 'safety' item. The test car was fitted with the optional 'adaptive light' cornering lights system that, at speeds of up to 45mph, directs an additional beam of light in the direction of travel when turning or cornering to illuminate parts of the road that would normally be missed.

In its latest TDI V8 guise, the A8 is a formidable player in the luxury sports saloon game. It's refined to a degree that no diesel has any right to be. Just to be crystal clear about this refinement business, when we say refined we don't mean 'compared to other diesels'. We mean compared to anything else with four wheels. That's how good
it is. It's also immensely satisfying to drive at any speed.

The A8 TDI is big, stylish and understatedly opulent. It comes with all the creature comforts most owners could reasonably ask for, including keyless access and start-up. Personally, I still prefer to physically turn a key in the ignition although in the A8 you don't even have to hold it once you've flicked the key. The engine automatically turns itself over until it fires. Never having to take the key out of my pocket to lock or unlock the car was definitely A Good Thing.

As too was the self-opening, closing and locking bootlid — operated by either the remote or a button in the boot or driver's door. And while it comes laden with state-of-the-art electronics, its MMI system — which unifies everything important into one easy-to-operate interface — is without a doubt as user-friendly as you can get.

The A8 TDI is as dynamically rewarding to hustle as it is to play the smooth-riding boulevardier — and it will even do 590 miles on a single tank of diesel! All that remains to be said is that, unlike Brando in On The Waterfront, this Audi A8 4.2 TDI will never be a contender. How so? Because it's already the title holder, is why. —
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Audi A8 4.2 TDI quattro | 58,420
Maximum speed: 155mph | 0-62mph: 5.9 seconds
Test MPG: 29.1mpg | Power: 322bhp | Torque: 480lb ft

--------------------------------------------------------- Audi A8 4.2 TDI quattro