By now you’ve probably read our reviews of the various new versions of Jaguar’s 2010 XJ.

If one thread runs through all of them, it’s the one marvelling at the unlikeliness of this car’s transformation from old-fashioned, old-English luxury conveyance to modern thoroughbred sports saloon.

To understand the completeness of this metamorphosis, you need to get stuck into a few of the gorey details pertaining to this great big Brit four-door.

For starters, the XJ’s got the same steering rack as an XFR; only its longer wheelbase and slightly softer chassis makes it any less agile than the smaller M5-basher.

Next, there’s a mass issue to consider: because an aluminium XJ Supersports actually weighs less than the largely steel, identically engined XFR. If it’s any slower, therefore – and it isn’t much slower – it’s because of the way the larger car’s drivetrain and running gear are configured.