For ages the Holy Grail of luxury-car recipes has been to somehow blend sumptuous richness with sleek high-tech sport. But rarely are the fruits of such compromise anything close to perfect. For instance, when attempting this blend, really sporty luxury cars tend to look thinly contrived when they try to be Olde-World traditional at the same time. Likewise for plush quasi limos that attempt any sort of athletic sportiness.

One of the few cars that's arguably pulled off this blend with deep genuineness is Jaguar's luxury flagship, the XJ8.

These big sedans are offered in base XJ8 and hotter XJR models on a 119-inch wheelbase, or in XJ8 L, Vanden Plas, and Super V8 versions with a 124-inch wheelbase. All are powered by a 4.2-liter V8. It makes 300 hp in XJ8, XJ8 L, and Vanden Plas or 400 hp in the supercharged XJR and Super V8. A 6-speed automatic is the only available transmission.

We recently got a week-long opportunity to test an XJ8 L, an experience that we truly savored from beginning to end. Indeed, when you park any XJ8 in your driveway, you immediately feel yourself standing straighter, shoulders squared, sensing the world looking at you with envy.

And that feeling isn't limited to the exterior. The XJ8's upscale vibe permeates the whole car. A pull on the hefty chrome door handle reveals a cabin swathed liberally in high-quality leather. That's complemented by deep, dark polished wood and tasteful hints of sturdy chrome trim.

Receiving much of the leather and wood is the dashboard, which remains basically true to the traditional Jaguar ethos -- organic styling, basic round gauges, and a minimum of gadgets.

But when we say "minimum" of gadgets, that doesn't mean there isn't any grandiose electronic stuff in the XJ8. The center of the dashboard is dominated by a multi-function display, which incorporates the audio, navigation, and climate-control systems. This screen is surrounded by two rows of buttons for operating it. The setup looks intimidating at first, but the array of switchgear actually simplifies operation by giving most common functions their own dedicated control, instead of relying on hidden touch-screen menus as many such systems do.

The seats have comfortable, supportive bolstering and the driver gets a position that's easily tailored for effective control manipulation. Head room in front and back seats is more than adequate even for very tall occupants. But the real treat of the long-wheelbase XJs is their copious leg room. Unless you're one of the lankier NBA players, there's a good chance your feet won't even get near any part of the front seat -- very refreshing.

The engine lights up with a pleasing timbre that's deep and strong, yet smooth and sophisticated. That personality carries beyond just the sound, aptly describing this V8's power delivery throughout the operating range. Although the naturally-aspirated version won't strain your neck with the stunning punch of its supercharged XJR and Super V8 sibling, this base powerplant nonetheless moves the car away from a stop with satisfying, unencumbered ease.

As potent as this engine is in typical city and suburban driving, it's on the highway that it really enters its element. Cruising along at 60 mph or more, the XJ8's V8 settles into an effortless lope, disappearing far into the background below conversation level. Then, with a quick prod of the accelerator it leaps into action, letting out an enjoyable growl and offering plenty of muscle for passing.

This is aided by the automatic transmission, which cooperates with swift, appropriate downshifts, particularly in its Sport mode. Drivers can also have a bit of manual control by using Jaguar's standard J-Gate shifter, which provides a second gate for the gear selector to move in, with detents for each gear.

That said, Jaguar's decades-old J-Gate concept has almost always gotten lukewarm reviews, and this incarnation of the design isn't likely to change that reputation. We give it an "A" for effort, but a "C-plus" for execution. The long shift pattern has second gear awkwardly all the way forward, with easily-missed detents providing a vague tactile indication of where you're at in the process.

But that's about the only really unsatisfying element of the XJ8 experience. And it does nothing to detract from one of the car's most pleasing aspects -- its ride. Supple and hefty feeling over practically any kind of pavement, the XJ8 L provides a serene environment for even the longest of trips.

In big cars like this, such extreme isolation from the road often makes for sloppy handling -- the soft springing generally employed to provide such a coddling personality tend to dull response. And the rigid construction required to make any car handle well can make large machines such as the XJ8 massively heavy, thereby further degrading handling.

But the XJ's lightweight aluminum construction allows the car to make an end-run around such floppy tendencies. The car responds to drivers' input with a sharpness that's surprising for such a big car. Body lean is well-controlled and grip is more than ample for some pretty rapid cornering work.

Additionally, the XJ's handling has some real soul. The steering is light, but it weights up pleasingly as cornering loads increase. And the sensations felt through the wheel are smooth and refined, yet provide good road feel for fairly aggressive corner entry.

Those are refreshing characteristics to find in a big luxury car. Piloting an XJ, you don't feel that twinge of uncertainty as you approach a challenging set of curves and start making decisions regarding line and entry speed. You can stay calm in the XJ -- you sense that you're getting plenty of good information about what the tires are doing.

But that's not really surprising when you think about it. Pretty much everything about an XJ projects that unmistakable air of confidence. Like the previous-generation XJs did for decades, this latest iteration of Jaguar's flagship never wavers in its genuineness. It remains the smooth-yet-sporty ideal that modern luxury cars have always wanted to be.

And despite rival brands' attempts, this cat will probably remain a breed apart for many years to come.