_P1What is it with car makers claiming they’ve invented new market segments? Porsche is at it, somewhat immodestly, with the Panamera, claiming that it launches the “Panamera class.”

As you probably know, the Panamera is a four-door, four-seat, fastback sports car at luxo-barge prices. Can’t see the “Panamera class” tag catching on, myself, but there’s merit to the concept. Aston Martin has followed similar lines with the Rapide.

The Panamera is really a grand tourer. Porsche’s thinking is that it sits somewhere between the Cayenne and 911 in concept, ideally with some of the practicality from the former and the dynamics of the latter.

In design terms that’s the theme too. In traditional Porsche style (one of the less demanding design studios to work in, I reckon), it’s a case of taking the shape you need, then adding Porsche cues – the sloping back, typical cut-out hood shape, smiling front air vent, you know the drill – to the form. And if it’s fugly, put it out anyway; they’ll get used to it. As we did with the Cayenne.

Initially, the Panamera comes with V8 engines derived from the Cayenne SUV’s units. In normally aspirated form that gives it fast-sports performance or, in the Turbo form you see it here, supercar-baiting potential.

Natural rivals? Think top-end versions of existing luxury metal. Cars like AMG S-classes or the Maserati Quattroporte. But if the Panamera reveals the latent dynamism it’s supposed to have, think also of smaller but more overtly sporting cars like the BMW M5, Mercedes CLS63 AMG and the Jaguar XFR. The Porsche, at 16ft long, is only 0.4in. longer than the Jag.

And on the good roads? It’s very able again, but let’s make it clear: on the Porsche scale, the Panamera edges closer to a Cayenne than a 911. Perhaps that’s no surprise, being a front-engined, four-wheel-drive four-door that weighs half a supermodel less than 2.2 tons. Because, given those constraints, what the Panamera does is extremely impressive.

You’ll want to take the suspension out of its softest setting as you go through four or five-tenths, moving the suspension settings through Sport and into Sport Plus. The Panamera firms itself up to the extent that Sport Plus might prove too harsh for some country roads; I can’t help thinking a Jaguar XFR would glide across surfaces the Panamera might pummel over, but on decent German roads it feels utterly planted, settling quickly over crests and lumps.

Sure, the Panamera never totally shakes off its weight, but it goes down the road at a proper lick and it steers very positively, with good precision and a rack whose speed increases further away from straight ahead. As in other Porsches, you don’t really notice this lack of linearity; it just means you can leave your hands where they are for most bends. And while there’s inevitably less steering feel than in the less assisted, lighter 911, there’s more than you’ll find in any other luxury sedan.

On the road, the high grip limit is sounded by a squeal from the outside front tire, though the electronically controlled rear differential (it brakes a lightly loaded inside rear tire, rather than being a proper limited-slipper) can help to straighten the Panamera on corner exit. Power always goes to the back and is apportioned (though there’s no set limit) to the front wheels as it needs it.

Press-on driving isn’t an experience that will blow your socks off, but the levels of control and pace that Porsche has managed to install into the Panamera are very impressive.

Is it the best performance luxury car to drive? Yes, although I’d defend anybody to the hilt who chose a Maserati Quattroporte instead.

Is it a proper Porsche? Yes, but if not by being totally engaging, then because its dynamism feels so absolutely indefatigable. Fitted with carbon-ceramic brakes, it stops on a dime, and its launch control (which Porsche says you are free to use as often as you choose because it’s less wearing on the clutch than a swift start with a regular manual gearbox) is a thing with which to wind up passengers for minutes, time and again.

The Panamera feels impeccably solid, stable and rigid. It’s a fine luxury performance flagship, and for plenty of people that’ll be enough. But – and there is a but – in this form the Panamera will lighten your fortune by $145,000.

I’ve talked about diminishing returns before, but does the Porsche really justify spending a Boxster’s worth more than a Jaguar XFR? I’ll reserve final judgment until I know whether it rides a backroad as well as the Jag, but to say I’d be surprised would be an understatement.

So perhaps this car does have something in common with the 911 after all. Because impressive though this Turbo is, I can’t help thinking the Panamera’s sweet spot is probably lower down the range.

Words: Matt Prior/Autocar