The difference represents a 291kg benefit over its major competitor, the BMW 7-series – sufficient to allow the Coventry luxury car firm to boast best-in-class operating economy and lower emissions figures in the upmarket F-segment.
But a leaner, lighter body structure also provides stunning driving dynamics to endow the new challenger in top-flight transport with the handling agility of a well-sorted medium-size saloon.
Brand manager Dermot Harkin said: ‘Most of the models we produce go to the corporate sector and we have put in a tremendous effort to create what we regard as the ultimate limousine for company chairmen and the captains of industry.
‘But I think there’s a good chance their chauffeurs will be pleased with it as well – and bosses will not be disappointed if they ever decide to take to the wheel themselves.’
After unveiling the LWB at the New York Auto Show earlier this year, Ford’s fast-growing premium car brand returned to the US for the media launch of the range it expects to account for 50% of global XJ sales from next year.
Harkin added: ‘Because it was part of the original design brief for the XJ, the LWB gets the full benefit of our new technology for manufacturing in aluminium. That means we have been able to extend the car by 4% at a cost of 1% in extra weight. ‘The result is absolutely no compromise in terms of performance, handling, steering and agility. I think this car drives so well that people will only ever regard it as a limousine when they sit in the rear compartment.’
Though it has a slightly taller stance from a 10mm higher roofline to maximise headroom, the LWB maintains the elegance and balanced appearance of the standard version introduced last year. Standing on big alloy wheels, it also has a sporty look.
Yet the longer rear doors allow easier entry and exit from a compartment that offers stretching room in armchair comfort and almost all the facilities of a club lounge.
Jaguar’s efforts to create a first-class comfort zone for its most affluent customers has called for lots of soft-grain leather, all piped and double-stitched, plus lavish amounts of burr walnut on doors and console inserts, all buffed to a mirror-like finish.
On the top-range Super V8, superbly-engineered trays fold down from the front seat backrests to provide space for laptop computers when the champagne glasses have been stowed away.
As an alternative to the supercharged V8, the Sovereign model reappears after a two-year absence. With the normally aspirated 4.2-litre V8 engine under its bonnet, this version reaches the benchmark 62mph rate in 6.6 seconds and shows a 3mpg economy improvement.
Boasting 16-way seats, DVD touchscreen, a power rear sunblind and Xenon headlamps, it is a higher-value offering and will be Jaguar’s most potent weapon against both BMW and Mercedes-Benz in the chauffeur market.
Harkin said: ‘Our brand has always been synonymous with solid value and we think the LWB Sovereign will be well received. Our aim is to use technology to empower rather than overpower and our touchscreen system controlling the air conditioning and entertainment options is a good example of making life easier for the driver.
‘Jaguar has an enviable reputation for producing cars with distinction, grace and pace. Now we’re adding more space.’
Behind the wheel
Jaguar’s recipe for more ample-size bodies of the automotive kind works surprisingly well in the new XJ LWB.
As a result of the company’s costly lightweight aluminum construction process, the capacious LWB is a pretty snappy mover. With such little weight penalty over the standard saloon, performance and economy figures are the same, which means the Sovereign has ample power for effortless progress.
The £11,600 premium for the supercharged Super V8 is a lot extra, but with 400bhp on tap, this is the version that’s so good to drive that it could cost the chauffeur his job.
For all that, the LWB impresses most when it is steered toward more demanding routes than motorways. The general agility of each version was impressive over the twisting backroads leading to California’s Nappa Valley wine region but the biggest surprise was waiting when we returned to San Francisco.
With a little help from former world champion racing driver Sir Jackie Stewart, Jaguar had set up a special handling course on a disused airbase.
For a limousine 5,215mm long, the twisting, snaking circuit seemed too tight to negotiate at anything other than a genteel rate, especially as it culminated in a tortuous slalom section calling for a dozen rapid changes of direction.
But the elongated XJ took it all in its stride, slicing through the switchback course with agility more akin to a Ford Focus than a limousine.
Stewart said: ‘This is a big car and it might be hard to accept that it can be so nimble and agile.
‘But weight is just as critical to good handling on the road as it is on the track. When you brake as you go into a corner, there’s a terrific transfer of weight to the front wheel on the outside of the bend. Reducing the load going onto that wheel makes a tremendous difference to the car’s handling agility.
‘Because Jaguar has come up with a lighter car, it achieves better handling and is able to change its direction quicker. I like it - and I doubt whether any of the company’s rivals would be prepared to have their limousines put through such a difficult course.’
Jaguar has a long pedigree in sporting saloons, but its latest LWB model is unique in feeling much like a GTI in a pinstripe suite. Even though computer-controlled air suspension provides the traditional silky ride quality, the car is the first to bring sports handling to the limousine sector.
|Model: XJ8 LWB||4.2 Sovereign||4.2 Super V8|
|Max power (bhp/rpm):||300/6,000||400/6,100|
|Max torque (lb-ft/rpm):||310/4,100||408/3,500|
|Max speed (mph):||155||155|
|Fuel consumption (mpg):||26.0||23.0|
|CO2 emissions (g/km):||264||299|
|Service interval (miles):||10,000|