Models tested:

2011 XJ 5.0 litre V8 supercharged, ZF six-speed automatic transmission (346kW & 575Nm) – $311,000

2011 XJ 5.0 litre V8, ZF six-speed transmission (283kW & 515Nm) – $259,000

Location: Hoover Dam, Lake Mead and the Valley of Fire – Nevada

The last time we got to test the latest XJ Jaguar was around the streets of Sydney, and that’s hardly appropriate for a limo size hotrod with a cracking 346kW and 575Nm on offer.

The long wheelbase version of the XJ 5.0 litre V8 supercharged Jaguar is a big cat – that’s 5.247 metres in length to be precise – and it likes to stretch its legs, so to speak.

Las Vegas, Nevada is dead flat – we’ve all see the opener to CSI – but surrounding the basin are the Sierra Nevada Mountains and mostly undulating rocky terrain. It’s up there in those mountains where you’ll also find some great roads that will properly test this vehicle’s abilities across wide criteria.

The Las Vegas Strip is only about 6.8 kilometres long from tip to tip, so within minutes we’re heading south on the US-95, US-93 towards the famed Hoover Dam.

Jaguar Design Director Ian Callum may well have created his best work yet with the latest XJ sedan, which was first released in 2010 and is already the winner of countless accolades including the UK’s Top Gear award for ‘Luxury car of the Year’.

While BMW, Mercedes-Benz and Audi have presented buyers with some superb offerings in the luxury large car segment, none of them come close to matching the sheer presence of the XJ – especially in long wheelbase guise.

Callum has clearly pushed the design envelope to the limit with the flagship model and in doing so, upset a faction of the old-school Jaguar club. But that’s just fine, because for every one of those traditionalists he put offside with this bold new design, there were another five new Jaguar customers who went into raptures over the latest XJ.

The English automotive press don’t mind bagging their own brands but Top Gear editor Jason Barlow described it best when he said about the XJ: “rarely has a new car slackened so many jaws”.

He’s spot on. There’s a tonne of money and wealth on the Vegas Strip and plenty of luxury kit on the roads, but all eyes are on the XJ whenever we stop for a photo op. It’s a beautiful shape, if not, a little Avant-garde, especially the rear of the car.

It’s not just the futuristic exterior design that works either. Callum has applied the same bold new approach to the XJ’s cabin, with a mix of Savile Row craftsmanship and high tech gadgetry such as the JaguarDrive Selector and the high-def Virtual instrument panel. Suffice to say, it’s a nice place to be when cruising on a US interstate.

The ZF six-speed transmission is silky smooth when either upshifting or downshifting and there’s so much low down torque on offer with this supercharged edition that overtaking in sixth is a breeze.

It’s not just the gear changes that appear seamless, so too is the effortless delivery of 346kW and 575Nm of torque (0-100km/h in 5.2 secs) that places the big Jag onto the top shelf of the limo mobiles. It’s a smooth enough ride in the rear seat accommodation for Callum to sketch the Jaguar sports car we’ve all been waiting for.

Barely out of Vegas and we’ve already reached our driver change point at the colossal Hoover Dam. This is no travel write-up, but if you ever get over this way, make a beeline for this place. As an engineering feat alone, it will blow your mind. Built more than 70 years ago, it still attracts around seven million tourists each year.

Next stop is the equally spectacular Lake Meade. It’s a by-product of the Hoover Dam and can hold a staggering nine trillion gallons (34 trillion litres) and stretches for 180 kilometres behind the dam.

There are some spectacular roads within Lake Meade Park, but they’re single lane and the blind crests encourage a cautious driving style. That said, it’s a perfect opportunity to connect up the iPhone and have a listen to any style of music you might fancy through one of the world’s best in-car audio systems – a 1200W Bowers & Wilkins unit that is guaranteed to sound better than any top-end in-home unit.

We’re on our way through the Valley of Fire and the roads are all but deserted so it’s time to see how Jaguar’s luxo express handles the pace through what are some very fast turns. There’s a noticeable difference in the road surface between here and Australia too. There are no potholes – not one! I guess that’s a benefit being smack bang in the middle of a desert with very low average rainfall, but seriously, whoever is laying our roads in Australia is taking us for a ride.

We’ve switched to Dynamic Mode to settle the car down at high speed through plenty of turns and the undulating terrain. There’s an immediate stiffening of the active dampers through the bends and the XJ has effectively morphed into GT mode. I mean I’m giving it a boot-full of throttle every time we hit a straight section of tarmac and I’m using the paddle shifters for extra pace before shifting cogs. There are pros and cons for both automatic and dual-clutch transmissions, but when shifts happen as smoothly as they do with this ZF, I can see why Jaguar still uses an automatic.

It’s easy to get a little carried away on these roads, but there’s a definite need to haul the car up before the blind dips or you could find yourself airborne, and we wouldn’t want that now would we?

Even at speed through the tighter turns, the XJ doesn’t lean. That’s the adaptive dynamics responding to both speed and lateral movement of the car.

Photo opportunities with a contrasting background don’t get any better than the Valley of Fire and the White Domes, and it’s also time to climb into a naturally aspirated 5.0 litre V8 XJ.

Down low, it’s not that easy to tell the difference between the two cars. There’s plenty of punch out of the gate, and 515Nm of twist is no small number. It’s also as much about the ZF transmissions, meaning the six forward gear ratios are particularly well spaced to get the most out of this V8 engine without the assistance of a supercharger. After all, 0-100km/h in 5.7 seconds for a car of these considerable proportions is hardly what I call ‘hanging around’.

There’s a good reason for that too, and it centres on weight, or the lack of it. Almost all other cars in this class weigh more than 2000kg, whereas this XJ variant tips the scales at 1773kg (kerb weight), or considerably less than the smaller XFR.

Jaguar employs its lightweight vehicle architecture for the construction of the XJ, which means mostly aluminium along with magnesium and composite alloys are used. The end result is both a lighter and stiffer body than any other car of this size and class.

It’s positively green too. Around 50 percent of the materials used in the construction of the XJ’s body are recyclable, and Jaguar announced at the car’s launch that there were plans in place to increase that number to 75 percent.

And if you’ve got any of those reliability concerns that were once the bugbear of the Jaguar brand, then you can rest easy.

In the well-known JD Power & Associates 2011 US Vehicle Dependability Survey Jaguar ranked number three behind Lincoln and Lexus. It was a strong result, but down from it’s number one position in 2009.

Jaguar’s XJ series is the standout car in its class. With ultra contemporary styling inside and out, and GT level performance and handling, it sits on a higher shelf than its competitors.