Hyde Park Corner was its usual jammed-up self yesterday morning. But as I gazed upon the scene of overheating metal, missed appointments and frayed nerves, I noticed something a little bit odd. Every single car on the entire roundabout was a big Mercedes-Benz.

Now I know Uncle Ken’s congestion charge keeps the poor out of central London and I know, too, that this is the time of year when celebrities come out of the closet to promote their latest book. So the demand for chauffeur-driven Mercs skyrockets.

I therefore peered from the back of my chauffeur-driven S-class into the others, hoping to catch a glimpse of Helen Mirren on her way from GMTV to a chat with Steve Wright. Or Kerry Katona perhaps, on her way from Fern and Phillip to Radio 5 Live to plug her new fitness video Fart Yourself Thin. Maybe I might even see Richard E Grant.

But no. Apart from James May on his way from Teachers TV to a shopping channel to talk about his new scratch’n’sniff book on armpits, most of the people in most of the Mercs looked fairly normal. Some were fat, some were thin, some were men and some were women. But they all had one thing in common. They’d been driven into a Mercedes because there’s absolutely nothing else on the market that will do.

I touched on this a couple of weeks ago while reviewing the new automatic version of Maserati’s Quattroporte. The amazing lack of choice for the fortysomething chap or chapess who just wants four wheels, iPod connectivity and a sepulchral silence from the engine.

The Maserati didn’t cut it at all. It was rough and fidgety and not at all what you might want after a hard day’s lunch. And it’s much the same story from anything else with a flamboyant badge. Astons, Ferraris, Lambos, Porsches. They’re all built for Lewis Hamilton. Not someone called Hamilton, who just wants to get to Lewes.

Even the people at BMW cock it up. They try ever so hard to make the 7-series big and soft and comfy. But like the naughty schoolboy who’s doing his best to behave, they just can’t help themselves. So, just as he sticks his hand in the sweetie jar, they stick their mitts into the “sports” bin and fit even the squidgiest 7-series with grippy, low-profile tyres and a suspension system that firms itself up for the bends.

This is tremendous, of course, if you find yourself at the Nürburgring being chased by the Four Horsemen of the Apocalypse in helicopter gunships. But if you just want to get home – which is more likely in my experience – the inherent sportiness would drive you mad.

Big Audis are similarly afflicted and while Lexuses are not, they can be quite bland. I sometimes think that if you stole a Lexus, you’d be able to drive it around for a year or two before the owner remembered that he had one, and that it was missing.

So, you might not want a Mercedes. You may not like Germans. But if you want something big, well made and above all, comfortable, you have no choice.

Really? Aren’t you forgetting something. I certainly was when I was driving that Maserati Quattroporte two weeks go. No really. I remember thinking: “Well, this isn’t good enough, so it’ll have to be a Merc.” But what about the Jaguar XJR?

Like the Maserati, it has a 4.2 litre V8 engine. Like the Maserati, it has four seats and 400bhp. Like the Maserati, many cows laid down their lives to create the interior, and like the Maserati, it is a handsome devil.

It was not always thus. When the new XJ series came along a few years ago, I was a bit shocked. It just looked like an old XJ that had got fat. But time, and a few styling modifications have been kind and now, in black, with those aluminium gills on the flanks, a wire mesh grille and some big wheels, the supercharged R looks absolutely, head-turningly stunning. Not as good as the Mazzer, I’ll grant you, but 2,454 times better than any Merc.

Better still, instead of a driver’s door, the XJR is fitted with a time portal. Step through it and you are taken back to about 1956. I cannot tell you how old-fashioned it feels from behind the wheel. There’s a big cat on the steering wheel boss but you think: “No, this can’t be. I’m in a Wolseley. Either that or somehow I’ve wound up in Queen Victoria’s knicker drawer.”

So, a little bit cramped, a little bit claustrophobic and faced with a big slab of timber, you set off half expecting the wireless to provide you with Raymond Baxter and not much else. You’re in a post office and the rest of the world is whizzing by in an e-mail.

Even the buttons and dials look and feel old-fashioned. But here’s the weird thing, almost everything you can fit to a Mercedes is fitted to the Jag. Yes, the switch for the heated seats look likes it came from a Baird Telecaster but push it and you’ll discover that it can not only warm your back but also, thanks to little air-con ducts in the fabric, cool you down as well.

Radar-guided cruise control. Yup, it has that as well and if you dive into the touchscreen command centre, you find it says Rear Multimedia. And never mind that it uses the same typeface as the Doncaster Gazette did in 1969.

What I’m saying is that with its television screens in the back, and its self-closing boot and its in-built telephone, the Jag has everything you ever use on your Merc.

Sure, Jag is owned by Ford, which has less money than most shelf stackers these days so one or two bits are missing. There’s no infrared night vision, for example, but unless you are a doggist, why would you want that in the first place? Similarly, the seat bolsters don’t punch you in the spleen every time you go round a bend – like they do on an M5 or in an Audi RS4 – but again, this is not something that’s desirable. Or even pleasant.

The Jag, in short, is fully loaded with all the stuff you need, and everything you don’t isn’t there. Noise, for example. I’m not suggesting for a moment that a Mercedes E-class is the Grateful Dead with windscreen wipers but the Jag couldn’t even make itself heard above a string quartet.

The XKR, it’s two-door coupé sister, has the same engine but makes a hell of a racket. The XJR borders on sensory deprivation.

And despite those big wheels and fat tyres it’s comfortable too. Really comfortable. Driving this is like floating on a lilo, on an oiled-up Thai teenager, in a warm bath, on a nice day, on a beach, in the tropics, while listening to Jean Michel Jarre. And that, come on, is what you want really.

You’d expect, of course, that a car this relaxing would be fairly hopeless if you were late for a plane. But no. It doesn’t handle, steer or brake quite as well as a Merc, or more particularly, a BMW, but it’s way, way better than the Maserati. And when it comes to oomph, Fritz had better be concentrating because Tommy Jag packs an almighty supercharged punch.

I suppose at this point you’re all thinking: “Yes. But I’m a busy man and Jags break down all the time.” Sure, that was the case when they were built by Red Robbo and his merry band of communists and lunatics. But you look at the customer satisfaction surveys now. Jag’s a player. Right up with the Lexus you bought last February . . . and lost.

Best of all, though, is what the Jag says about you. A Merc says you’re a chauffeur and that you have Lee Ryan from Blue in the back, talking about his new range of hair product. A BMW says you won’t let anyone out of a side turning. An Audi says you’re big in cement, a Lexus says you’re a bit boring and a Maserati says you’ve gone nuts.

A Jag, though? Well, you could be a government minister, or you could be Arthur Daley. You could be Hannibal Lecter, or you could be the chairman of BP. You could be anyone. But whenever I see a Jag, don’t ask me why, I always assume the driver has a gun in the boot. That makes you look a little bit cool.

Cool, and when you’re stuck at the lights surrounded by a million Mercs, a little bit smug as well.

Vital statistics

Model Jaguar XJR 4.2 V8 Supercharged
Engine 4196cc, eight cylinders
Power 400bhp @ 6100rpm
Torque 408 lb ft @ 3500rpm
Transmission Six-speed automatic
Fuel 23.4mpg (combined cycle)
CO2 289g/km
Acceleration 0-60mph: 5.0sec
Top speed 155mph
Price £60,252
Rating ****
Verdict Refreshing change from a Mercedes

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