FORGET the Seven Wonders Of The Ancient World – why the big Jaguar sedan doesn’t sell is the XJ-8th Wonder of the Modern World.

We’ve always regarded the current model as a bit of an anti-Dorian Gray – old looking (but devilishly handsome nonetheless) on the surface and yet youthful (and extremely high tech) underneath.

So while people constantly admired our test car – a blue XJ 3.5 fitted with a new base V8 engine, each one qualified it by remarking: “But I can’t drive that – it’s an old person’s car.”

Old person’s car indeed we grew tired of explaining the aluminium body, computer-controlled air-sprung suspension, advanced electronics and up-to-date drivetrain in a car that – in most people’s eyes – looks like the sort of car that Little Britain’s Sir Bernard Chumley would drive.

We think that Jaguar’s “facelift” attempt is akin to trying to put new exterior detailing on a Victorian weatherboard house. It just looks out of place, with the new rear bumper in particularly looking like a full nappy.

Yet despite the incongruous side power vents in the guard, or the out-of-place front bumper design, or loss of some exterior chrome detailing, the XJ remains beautifully proportioned, even elegant, in a way that no other luxury rival in the world – except perhaps for its Range Rover Vogue cousin – can compete with.

Perhaps one day people will better appreciate this car’s soft and warm beauty in the light of cold harsh Teutonic design.

But we doubt the interior will receive such a warm welcome, despite being very good in parts.

The annoying bits first: too-small instrumentation, with a speedometer featuring numbers in too-high an increment for easy reading – a digital supplementary speedo readout is badly needed here.

We hate the low resolution of the centre screen, with its bad pixilation and clumsy design. The buttons immediately below and either side of the screen feel hollow and cheap (but inexplicably not the ones above) or anywhere else on the unfashionably slabby dashboard), and... that’s about it. Everything else about the XJ’s cabin is all class.

Great front seats that adjust every which way and offer more than enough room are a great start to a very relaxed and sumptuous interior experience. They support for hours on end, provide immediate comfort, and look the part too.

The double-glazed windows certainly do their bit to keep the outside environment encroaching inside, while rich leather trim that is beautifully stitched, and excellent fit and finish equal to that of any rival are backed up by the quality wood trim, thick carpet and a real feeling of solidity.

Jaguar says it has fitted slimmer front seats that liberate more back seat space, and in the short-wheelbase model we tested, we found no reason to doubt this. Legroom certainly seemed adequate for most adults, and the two sculptured fixed backrests provide ample comfort and support.

Our test car included heated rear seats, retractable door sun blinds and a centre armrest-sited audio control unit. All worked brilliantly.

And so does the silky smooth drivetrain.

The 3.5-litre AJV8 replaces the old Ford 3.0-litre V6 petrol unit. Jaguar claims it is more economical as well as significantly more powerful and smoother, and we are not about to disagree.

First off – the fuel consumption average of 12.8L to 13.5L/100km in mostly inner-city driving is astounding for a car this large and salubrious.

The luxury of efficiency and economy is at work here, no doubt due to that lightweight aluminium body that does so much to contribute to the XJ’s special driving experience. This car weighs less than all but the base model Toyota Aurion.

That it sounds like a rorty V8 when pressed is fantastic news too. Yes, when mooching about serenely the drivetrain is but a distant hum, aided by that marvellous ZF six-speed automatic gearbox.

But flex your right foot and – unlike the old V6 – the bent-eight powerplant responds eagerly, building up speed quickly and with authority.

So the ASL speed control button comes in extremely handy, especially as that lazily presented speedo gives you but a hazy idea of what exact speed you are doing. In this day and age of pinpoint speed camera technology, this is just unacceptable.

Sitting on Jaguar’s CATS suspension, the ride is – as you might expect with a car using air springs – supple and absorbent. No surprises there.

But while the steering is a little on the disconnected side and low speed manoeuvres reveal some bodyroll, the shock here is that the harder you drive the XJ, the more composed the car becomes, hunkering down to provide a level of poise and cornering fluency that is totally at odds with the slippers and pipe styling.

Nicely modulated brakes haul the Jaguar up with absolute ease, while at speed there is a rock-solid solidity and stability to the car that leaves you in no doubt about what this car was designed to do – haul people across countries in speed, comfort and security.

Yes, a BMW 7 Series and Mercedes S-class do feel tauter in body and vehicle control, but the former especially errs too much on the firm side for it to be relaxing and laid back – a couple of qualities people seek from their expensive luxury saloons.

More boot space would be welcome though – the cargo area may be vast in length and width but it’s also disappointingly shallow.

But shallow is something the XJ 3.5 V8 resolutely is not. There is depth to this car’s engineering and quality that allows it to rise rather effortlessly to near the top of its class.

Observing the competition, the base big Jaguar undercuts its Mercedes S-class, Lexus LS460 and BMW 7 Series rivals by at least $20,000, while the equivalently powered Audi A8 3.2 FSI quattro is heavier and lacks two cylinders.

Whatever you may think of the exterior styling, the interior has dated rather more quickly than we would have liked, especially after the XJ’s striking XF baby brother’s fine efforts.

Unfortunately, it is enough to put many people off a wonderfully characterful and accomplished luxury sedan.

And we are not talking about characterful as a euphemism for unreliable or temperamental either. This Jaguar has, well, the lion’s share of the personality compared with any one of its German and Japanese rivals. Only the $269,000 Maserati Quattroporte has anything like this car’s appeal, but that’s like comparing Sean Connery with Sophia Loren.

Now back in Jaguar’s clutches, we missed the XJ from the moment it left us. There is a feeling of richness, space and textured quality on the cocooning inside, advanced technology at work underneath as it traverses effortlessly over the earth, and timeless beauty when drinking in the lines from the outside. And while you don’t see nearly enough on the street, the XJ’s exclusivity makes it stand out while marking you out as an individual.

All of the above – collectively – define luxury for us. So, as we said, why more people don’t choose the XJ is a puzzle.