John Simister previews Jaguar's attempt to update its image with the remodelled XK

That's the difficult bit. And, obviously, the ALC was a preview of how the next XK was going to be. Everyone knew the almost decade-old XK8 and XKR were ready for replacement. All that remained unanswered was how much of the ALC's design would make it to production.

Waddesdon Manor, Buckinghamshire, May 2005: a secret gathering of motoring writers sees the new XK in pre-production form. First it passes by at a distance, its V8 engine sounding encouragingly racy, then it arrives in the courtyard. It's very much like the ALC, but with round front foglights and a toning-down of the metallic details. The vertical air vent behind the front wheels remains, however, its simplicity spoilt by an afterthought badge.

Some eyebrows are raised at the complexity of the light lenses, both front and rear. The idea is to provide a talking point, which is certainly achieved.

Goodwood Festival of Speed, July 2005: the same XK makes a fleeting public appearance in a run up Goodwood's hill-climb. The reaction is very positive.

Now, just before the Frankfurt Motor Show, we can reveal more details of the new XK, which goes on sale next March in coupé and convertible versions. These will have 4.2-litre V8 engines, delivering a useful 298bhp. A 3.5-litre V8, plus a supercharged V8 for the XKR version, will follow in 2007.

One of the XK's key points is its weight. At 1,595kg it's 120kg lighter than the outgoing XK and 190kg lighter than its Mercedes-Benz SL500 rival. It achieves this with its bonded, riveted and welded aluminium construction. The benefits are clear: the coupé is claimed to reach 60mph from a standstill in 5.9 seconds, just half a second longer than the outgoing XKR.

The bodyshell is 30 per cent stiffer, too, which should give a tauter, sportier drive without spoiling the ride comfort. This should be as true of the convertible as of the coupé.

"We designed the structure as a convertible," says the engineering guru Mike Cross, "then added the coupé parts."

Thanks to new pedestrian-protection legislation, there has to be an absorbent space between the bonnet and the top of the engine, which is leading to some bulbous-nosed new cars. Not the XK; using fibre-optic sensor technology to detect an unfortunate pedestrian, it flips up the rear edge of its bonnet by 170mm on two airbags.

The overall shape is still Jaguar-curvy, but there are definite edges . The corners are heavily chamfered, too, which reduces the impression of weighty overhang when you see the XK from an angle, Instead, the body seems to end just beyond the wheels.

Inside, textured aluminium is the standard decoration with two types of wood as options. The cabin has room for two small children. The gear selector - all XKs will be six-speed automatics - no longer moves in a "J-gate" and there are paddles on the steering wheel for manual selection. As in the Aston Martin DB9, the transmission blips the accelerator during a downshift to give a smoother, racier shift.

Sounds good so far. Read the truth in next February's road test.

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