Price: £64,400
Top speed: 155mph 0-60mph 6 seconds
Consumption: 40.1mpg
CO2 emissions: 184g/km
Best for: Refugees from German prestige brands
Also worth considering? Audi A8, BMW 7-Series, Mercedes S-Class

If you're explaining, you're losing. That grim piece of wisdom comes from the tough world of American political campaigns, where having to waste time clarifying a candidate's mis-statements, or getting an over-complicated message across, can lead to electoral death. One day last summer, it occurred to me in a different context. The occasion was an early viewing Jaguar put on in London for its new large XJ saloon, and the man doing the explaining was the company's design chief, Ian Callum. He was walking around the car, pointing out different aspects of the XJ's shape, lifting the lid on some of the techniques he and his team had used to achieve particular effects.

It didn't really seem to be that desperate sort of explaining you do when you're losing; in fact it was probably the most absorbing and informative talk I've ever heard from a senior motor industry figure. And yet there did seem to be a few things that needed explanation – those black strips covering the rear window pillars, for example, one of the elements which at first sight make the XJ appear a fussier design than the superficially similar XF. They, it was said, alleviate the visual heaviness that might otherwise creep into a four-door fastback shape, but I couldn't help thinking that the beauty of any object should immediately be apparent to the eye of the beholder, rather than having to be explained by its designers.

Several months later, I had another chance to hear Ian Callum explain the XJ's looks, this time at its launch in Paris. There, he shared another of the car's secrets. If I understood it correctly, it was this: elements of the XJ's design, while novel, conform to deeply established rules of proportion. Even if they at first appeared awkward, they would, therefore, with familiarity, come good. At the time, I was sceptical; now, I have to admit that he was right. When I first saw the XJ, I thought it was handsome but fell slightly short of true greatness; now, after looking at it in pictures and in the metal for the best part of a year, I think it is the most beautiful car in the world. The fact that it performs sensationally well in almost every respect is a bonus.

The burden of explanation is lifted from Mr Callum's shoulders and now weighs heavily on the design departments of Jaguar's German rivals. The XJ makes their big saloons look ordinary; they're losing and they have some explaining to do.

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