Conventional wisdom dictates that a coupe has two doors, occasionally three if you count a hatchback. Five doors, as boasted by the Mazda RX-8 are pushing things a bit. A quartet of doors is the one attribute that really precludes entry to the coupe club. Possessed of four doors, you are usually a saloon. Saloons, as we all know, are generally a bit boring, driven by middle management and chubby gentlemen the world over. The Mercedes CLS breaks that particular mould. It's breathtakingly striking with flowing coupe-like lines, razor-edged detailing and superb finish. It also has four doors.

Walk around a CLS and - if you're a student of automotive design - you may well feel a gnawing sense of unease. What is it about this car that's so unusual? Yes, a four-door coupe isn't exactly conventional but that isn't it. After a while the realisation dawns that the CLS just plain doesn't seem like a German car. History has taught us that German cars feature clean, pragmatic styling. Even the more extrovert and successful German designs, such as Audi's TT, have a pared-down industrial hygiene to the styling. The CLS is different insofar that it is unashamedly Baroque, with an attention seeking ostentation suffused throughout it. In short, this car looks American.

The suspicion is well founded, the CLS being largely the work of American stylist Michael Fink. Priced from £43,957, it almost looks like an evolution of a Los Angeleno low rider from the late fifties and is undoubtedly going to be a very hot ticket in Mercedes' biggest export market. It's difficult to take in all of the details of the CLS styling at one go. The way the twin swage lines that run along the flanks become the leading edge of the front wheelarch is beautifully resolved and the big L-shaped front lights mark a welcome departure from the gawky 'peanut' headlamps seen on so many contemporary Benzes. Even the door handles look like something from an Art Deco design exhibition.

"History has taught us that German cars feature industrial, pragmatic styling. The CLS must have ditched history class early"

Open the door and the surprises continue. In true coupe fashion the CLS features frameless glass, the windows dropping a centimetre or so as you pull the handle. It's also a long way down to the driver's seat. Stand next to the CLS and you'll soon realise that it's a good deal lower than either a CL or a CLK coupe, the two big hitters of Mercedes' coupe range. The cabin is like no Benz currently offered, the fascia being particularly reminiscent of modern Jaguars. A vast plank of wood runs across the dashboard, punctuated by the ventilation controls and a deeply sunk instrument binnacle. If imitation truly is the sincerest form of flattery then Jaguar should be coyly blushing, rather than rushing to issue writs.

The CLS is a four seater with a chunky transmission tunnel dividing the two rear seats. It's easy to forget that there's an additional set of doors at the back, despite Mercedes not adopting Alfa Romeo's clever hidden handle feature. Once opened, taller passengers will have to watch their heads as they climb in, but the legroom isn't bad at all. Compared to its closest rival, BMW's 6 Series, the CLS is a far more practical proposition. Headroom in the back is 37mm down on the E-Class saloon but is far from problematic although the high waistline gives a slightly claustrophobic feel. The fact that it's easy to get in and out of the back helps here.

Three petrol engines are offered to UK customers. The smallest petrol powerplant is no slouch, being the 268bhp 3.5-litre V8. This CLS350 has a price tag of £43,962, which looks attractive in comparison to the other Mercedes models using this engine. An S350 saloon, for example, is over £56,000, an SL350 over £61,000 with only the compact SLK350 undercutting it. Mercedes predict that this will be their most popular model and although they claim to be aiming at 30,000 CLS sales across the globe in 2005, company insiders are so excited about the concept that they'll be disappointed if the car doesn't shift 50,000 units.

The CLS350 will get to 60mph in 7 seconds and run on to an electronically limited top speed of 155mph, which means that it's quick enough to keep a BMW 630i honest. The CO2 emissions are pegged at a relatively saintly 238g/km and a combined fuel figure of 27.9mpg is good news for those who don't want to be saddled with a gas-guzzler. If you've got a little more money to throw at a CLS you may well be tempted by the V8 engined CLS500. Here you get a couple of extra cylinders, a fraction better refinement and acceleration which seems a rather questionable return on what is the thick end of a £10,000 premium. If you really hanker after a CLS that will lift its skirts and fly, best go for the CLS63 AMG version. Expect to see it featuring prominently in rap videos on MTV soon. The sole diesel option is also the cheapest CLS available. £43,957 buys you the 224bhp 320CDI which can hit 60mph in 7s and with 500Nm, it feels quicker in real world driving than the 350. Fuel economy of 37mpg is not to be sniffed at.

Marketeers would dub the Mercedes-Benz CLS a 'high involvement' car. It's a car to which it's possible to form an emotional bond, attracted by its exotic styling and unconventional attitude. This makes it a very special car. When was the last time you could form such a bond with a Mercedes. You could admire a Mercedes, aspire to one, or respect what they did but the three-pointed star was never something that would tug on the heartstrings. The CLS changes that, and this is in part why it's such a culturally disorientating car and one with such a big capacity to surprise. Henceforth, four-door coupes are set to become rather more appreciated.