BMW Z4 M-Roadster

There is no doubting that the M Roadster makes a strong visual impact. The uninitiated or uninterested will see little that sets it apart from the rest of the increasingly ubiquitous range, but for those in the know the modest styling changes are an instant indication that this is the car they have long been waiting for, a car with significance and status.

Besides the gleaming 18-inch alloys, a deeper front air dam, front spoiler, two twin-exhausts and the addition of a pair of sharp bonnet creases lend the M Roadster a subtle but distinct edge of aggression over its less rarefied Z4 counterparts. It works. But this car is not only a looker, it's also outrageously quick.

Find a stretch of road that is bereft of scooters, pensioners or the sherry-addled insane, and all that attention becomes suddenly insignificant. The M Roadster will leave them for dead.

The current (as in outgoing) generation M3 provides the power, some 343bhp, from its 3.2-litre straight six, but in a car that weighs a comparatively modest 1,485kg. A sprint time of 4.7secs to 60mph and the inevitably limited 155mph top speed are actually fairly meaningless, though.

What impresses with the new M Roadster is its astonishing in-gear acceleration. With 232lb ft at 4,900rpm, there is just enough torque to keep up a constant, blistering pace, and with peak power not reached for another 3,000rpm, the overbearing impression is that there's always more grunt within than space without to exploit it.

In fact, this is where the M Roadster begins to show its true colours, not in its ability to build speed, but in its inability to find anywhere appropriate to do it.

Unlike the more realistic prospect of an M3 or M5, cars with as much focus on practicality and distance capability as brutal performance, the compact, two-seat M Roadster exists purely as entertainment, a car in which you hunt out quiet B-roads like some horsepower vigilante hell bent on avenging the congestion of every inch of major asphalt. Think AC Cobra, and you are someway to comprehending this beast.

Yes, there's a reasonable amount of boot space, and the cabin isn't what you'd call cramped, but this is not the car for a daily commute. So the M Roadster becomes very specialist, more so than its luxuries and equipment would imply.

Take into account both the turn of speed and £42,750 price tag, and you've got a car that only a very select few will be keen or wealthy enough to either buy or readily appreciate.

BMW's M Sport engineers would rubbish this point, citing the time, expense and technology that have been pumped into making the M Roadster such an astonishingly rapid car, but the rag-top buying public may see things a little differently.

They want windy motoring, they want BMW's badge on the boot lid, and unless they've come by their money in a way that has immersed them in an overwhelming sense of guilt, they want it as cheaply as possible. Then, the general public are not bon viveurs.

The sort of people who will be tempted into M Roadster ownership are going to like the little styling changes and the hallowed 'M' badge. They're also going to love the exhaust note that sounds like a rabid Rottweiler barking from the depths of hell.

Just what the M Roadster is all about is neatly illustrated by the 'carbon-structure' leather dash trim. Apparently BMW's customers want the idea of weight-saving carbon fibre in their sports car, but still with the luxury of lots of heavily stitched hide. So they get it.

It looks all right initially too, but give it a moment's thought and you begin to see a mixed message. This is a fabulously fast and accommodating car, but in trying to juggle the need to maintain the 'M' legacy with customers' expectations regarding comfort and luxury, it becomes both quicker and pricier than most people can handle. It is the embodiment of bon vivant principles in an automobile that is already a modern day classic.