Back in the year 2000 as the world struggled with the Millenium Bug, German prestige brand Audi was struggling with a lack of foresight.

Having virtually pioneered four wheel drive in ordinary road cars with their clever quattro system, they'd failed to foresee just how popular it would prove to be in big, chunky SUVs.

As a result, by the turn of the century, while rivals like BMW and Mercedes were racking up sales with X5s and M-classes, Ingolstadt was getting left behind, its own Q7 SUV still years away from launch.

A stop-gap was needed - a car like this one, the Audi A6 allroad. The allroad was an Audi A6 Avant estate with clever air suspension for limited off road ability and a little more styling attitude.

A simple enough idea you might think, except that at the time of this brilliantly executed model's launch, no one else had thought of it.

This concept was continued with a second generation model in 2006 and further evolved with the MK3 version we look at here, launched in the Spring of 2012.

By then, Audi had of course long since properly plugged the SUV-shaped gap in its line-up with Q3, Q5 and Q7 models.

But by the 21st century's second decade, almost any brand could sell you an SUV.

This A6 allroad, in contrast, remained a largely unique proposition, not properly copied by Mercedes or BMW until well in this 'C7' design's production run. Of course, the market has long offered slightly smaller SUV-style all-wheel drive estates than this: Subaru has been doing it for years and Audi launched its own A4 allroad model in 2009.

But these models basically offer nothing more than plastic body cladding and a marginally higher ride height, this A6 allroad does the job properly, with an air suspension system able to raise the car height enough to give it real off road ability.

Such has always been the A6 allroad's appeal, the car of choice for the clever few who realise they don't need a hulking great off roader for the style of sensible SUV-ness.

And in third generation guise? Well, the recipe was further refined, with a more powerful range of more efficient 3.0-litre V6 engines and enough high technology to satisfy the most committed technophobe.

The original 204 and 245PS versions of the 3.0 TDI engine were updated respectively to 215 and 268PS by 2014.

This 'C7'-series A6 allroad model sold until late 2019, when it was replaced by a new fourth generation 'C8'-series version.

Just a glance at this third generation 'C7'-series A6 allroad is enough to confirm that things have come a long way from the rather crude plastic cladding that defined the look of the first generation version.

Like the MK2 'C6'-series model, this one was a subtle evolution of the line - and a larger one too.

To give you some idea of the scale of this thing, its extra 6mm of length over the previous C6 design upped the total length of this model to a fraction under five metres, enough to make it fully 150mm longer than a huge Range Rover Sport, so you might need to double check that it'll fit in your garage. In terms of height as well as length.

This allroad, after all, sits 60mm higher than an ordinary 'C7'-series A6 Avant, but that of course isn't the only difference.

The chrome effect grille is the first thing you'll notice.

Then there are contrasting wheel arch extensions, which original owners could have painted in body colour if they really wanted to disguise this car's SUV-ness.

A stainless steel underbody guard overlaps into revised front and rear bumpers and there are aluminium roof rails.

The more important stuff though, is under the skin where use of aluminium for up to 20% of the body weight enabled this generation allroad to shed as much as 70kgs over the previous model. This MK3 model was lighter then, even if it was larger - and the extra size is something you'll appreciate jumping into the rear.

Much of this design's additional 72mm of wheelbase was used for the benefit of back seat passengers who as a result enjoyed an extra 7mm more of head room.

It's still a bench primary shaped for two adults, though three children will be quite comfortable.

Behind lies a capacious 565-litre luggage bay that was 20-litres bigger than that of the previous model.

Should more space be needed, you can flip the rear seats down to access up to 1,680-litres.

Up front, the seats are 20mm further apart than they were in the previous generation version: it's much as you'd find in a conventional A6 Avant - which is certainly no bad thing.

The build quality is typically impeccable, from the leather work on the seats to the attention to detail of the damped handles and covers.

The piano black trim parts have even been treated with a UV-resistant coating to keep them from fading in fierce sunlight.

Most of the minor controls are gathered on and around the steering wheel and it's all surprisingly easy to use given the complexity of this car's systems.

The MMI infotainment system improves in its user friendliness with each generation and features a pop-up screen which is bigger and clearer than before and allows for a sleeker dashboard profile.

Please contact us for an exact up-to-date valuation.

It's very unlikely that this A6 allroad will have been seriously used off road, but check underneath just in case.

This 'C7'-series A6 generally has a good reputation for build quality and reliability, but there are a few things you'll need to look out for.

We've heard reports that the electronic handbrake can sometimes get stuck.

The infotainment screen that should power smoothly out of the dash top on start-up can sometimes get stuck too, so check that.

Apparently the lock on the fuel filler cap has a history of sometimes breaking, so check that and make sure it opens properly.

On a few 3.0 TDI models, you might notice an engine rattle; faulty chain sensors are the cause, an issue solved when Audi introduced new chain sensors for this engine in 2016.

If you're looking at a 2014 or 2015-era A6 3.0 TDI and it has the rattle, then this can apparently be solved by the fitment of these revised chain sensors, something your dealer can arrange: ask if it's been done. We came across a few reports of the electronic steering needing software updated.

And with air suspension, the wishbones can apparently occasionally creak, especially over speed humps and potholes.

This can, it seems, be fixed by installing wishbones borrowed from an Audi RS5; yes, really.

Audi's quattro 4x4 system should prove reliable and the engines have all been used extensively in other Audi models so there should be little cause for concern there.

Look out for interior scuffs and alloy wheel scrapes.

Otherwise, you shouldn't have much to fear, even from a high mileage example.

(approx based on a 2015 A6 Aallroad 3.0 TDI 245PS - Ex Vat) An air filter costs in the £13 to £21 bracket, an oil filter costs between £7-£11 and a fuel filter costs in the £15 to £26 bracket.

Front brake pads sit in the £40 to £75 bracket for a set - or £30-£80 for rears.

Front brake discs sit in the £114 to £247; for a rear pair, you're looking in the £77 to £147 bracket.

A water pump costs in the £38 to £58 bracket.

A radiator costs around £173, a headlamp costs in the £143 bracket.

A pair of wiper blades cost in the £27 bracket.

Air suspension.

That's what an A6 allroad is all about.

That's what differentiates it from an ordinary A6 Avant.

And that's what sets it apart from its key rival, Volvo's XC70, as well as more compact 4x4 station wagons with off road pretensions like Volkswagen's Passat Alltrack, Skoda's Octavia Scout or Subaru's Forester, models that are really little more than jacked-up estate cars.

The air suspension settings can be controlled via the Audi drive select system and can be switched between five different on road modes, according to your driving situation. There's 'Dynamic' for press-on driving and 'Comfort' for laid-back highway trips, but having played with these, most of the time, you'll probably leave things in the 'Auto' setting, which uses a series of sensors to attempt to gauge the best mode for any given condition and can even automatically drop the car for more efficient high speed cruising.

That'll be one of the ways that the dedicated 'Efficiency' setting helps to lower your running costs and global footprint, focusing, as it does, all the electronic systems on improving fuel consumption.

And you might like to fiddle with the 'Individual' mode, which allows you to choose the favoured parts of other settings for your ideal set-up. So it's possible to set this Allroad up to be a fairly soft, high-riding thing or a nicely hunkered down vehicle that thanks to its torque vectoring system, really doesn't corner too badly - and would manage even better if the electromechanical steering system Audi developed for this 'C7' generation A6 offered a bit more feedback, something lacking even in the 'drive select' system's sportiest mode.

Thing are a bit better if you get an A6 allroad whose original owner paid extra for a 'dynamic steering' system that can adjust the steering ratio to the speed you're going.

Some original buyers paid even more to enhance the standard quattro 4WD system with a 'sport differential' that can vary torque distribution between the rear wheels to optimise grip through the corners and fire you from bend to bend.

It's all intended to emphasise the way that this car can provide a far more car-like driving experience than any SUV. Jump from a Discovery, a Mercedes M-Class or even a BMW X5 into one of these and you should find the handling and responses to be a revelation.

The ride's better too, provide you get a car whose original owner didn't hobble the car with an optional set of larger 20-inch alloys.

But none of that would matter very much if this Audi were unable to cope off road.

Fortunately it can.

Head off the tarmac and your fingers will head to the drive select system again and its 'allroad' mode, which raises the body for off-road driving by 35mm.

If that's not enough, a further 'Lift' mode adds another 10mm of height, bringing your distance from the ground to 185mm for those occasions when you really need all the clearance you can get.

The first generation version of this car could ride a lot higher than that and compete with fully-fledged SUVs featuring 200mm or more of ride height.

Audi's more recent research though, indicates such capability to be unnecessary.

There aren't many buyers who'll take this car off road at all and those that do tend to take the view that really extreme terrain isn't the place for it.

Having said that, you'll be able to travel a surprisingly long way in the wilderness before finding something that'll defeat this allroad.

Indeed, with a set of winter tyres on one of these, we reckon that most of the time, you'd be almost unstoppable.

All right, so there's no low range transfer case of course, of the sort you'd get on a fully-fledged SUV, but you do get a mechanically self-locking centre differential and hill descent control to walk you carefully down steep slopes.

The off road-tuned ESP stability control and the pretty generous approach and departure angles (18.3 and 20.3-degrees) will also be helpful and you can view the angles of pitch via a special function on the MMI infotainment system.

There's also a capable 300mm wading depth.

And the peace of mind of knowing that should you find yourself somewhere you shouldn't be, a sturdy steel under body guard should help you power carefully out of trouble without serious damage. Ah yes, power.

Here, there's all the choice you could want - providing that's a 3.0-litre turbocharged V6 of some kind.

The A6 allroad offers a choice of four such units, the least relevant of the quartet being the 310PS TFSI petrol engine that virtually all original UK customers elbowed aside in favour of a diesel.

Most were tempted by the entry-level 204PS 3.0-litre TDI that manages 60mph in 7.2 seconds and will knock on the door of 140mph where conditions allow.

Next up is the 245PS version of this engine, which steps the torque up from 450 to 580Nm, drops the 60 sprint time to 6.6 seconds and tops out at 145mph.

Like the petrol variant and the lower-powered diesel, drive is transmitted to the tarmac via a super-smooth twin-clutch seven-speed S tronic gearbox. It's a great package but, if you can afford it, the top variant offers an even better one.

The 3.0 BiTDI variant was flagship of the C7 series A6 allroad range, an engine featuring two series-connected chargers that together generate so much torque - 650Nm from just 1,450rpm - that Audi had to fit a sturdier 8-speed automatic gearbox to cope.

With 313PS on tap, 62mph from rest is just 5.3s away, but at any speed, the merest touch on the throttle is enough to hurl nearly two tonnes of Vorsprung durch tecknic purposefully towards the horizon, accompanied by a brilliant roar amplified by the sound actuator that some enthusiast at Ingolstadt decided should be placed in the exhaust.

Use this as a vehicle for your next ski trip and there's not a lot that's going to beat you onto the slopes.

British roads are routinely rated as the worst in Western Europe and made worse by an average of 184 wet days every year, mostly throughout winters that climatologists claim are set to get more unpredictable, with higher likelihoods of snowfall.

High fuel prices and spiralling taxation rates make that a difficult challenge to meet in an SUV.

So an all-wheel drive estate car with elevated ride height that's right for the rough, efficient to operate and beautiful to ride in seems to be the perfect car for well-heeled British families.

This 'C7'-series third generation A6 allroad estate meets that brief perfectly. A6 allroad buyers are apparently the most affluent of any of Audi's customers, so it makes sense perhaps that they're also amongst the cleverest, amongst the few choosing a car with four-wheel drive for what they actually need it to do, rather than buying into vague perceptions of safety and social standing.

There are other biggish, plush estates that offer limited off road ability of course, but without the clever air suspension that really makes this car work in that respect, these can seem very pretentious and contrived. No, if you want the occasional benefits of better ground clearance and off road traction without the usual clunky dynamic downsides.

If you can do without the image, expense and bulk of a fully-fledged SUV.

And if, in summary, you want to make a sensible lifestyle statement, then we can't think of a better way to do it.