For more than 20 years, the BMW 3-Series Convertible has been the aspirational rag top for those who want to look cool. But, as Nigel Burton reports, the new version is very different.

BMW didn’t get where it is today by ignoring market forces. For years, BMW engineers have poured scorn on the concept of a folding metal roof for a convertible car.

They laughed when the idea first appeared on the Mercedes SLK. A metal roof was too heavy, they said. The weight was in the wrong place and it adversely affected the car’s handling. Why would anyone bother?

Since then there has been a stampede among car manufacturers to offer folding hard-tops. Buyers weren’t swayed by engineering problems; they revelled in the extra protection offered by a metal roof and loved the cool way their cars’ roofs folded the panels and then hid them in the boot.

Sales of traditional soft tops dropped faster than a folding steel roof.

So it’s hardly a surprise to find the fourth generation 3-Series Convertible breaking with tradition by replacing the fabric hood with a steel three-piece affair which can go from coupe to convertible in less than 23 seconds.

Another reason BMW resisted the folding hard-top concept was the compromises it placed on a car’s looks. The need to accommodate so much metalwork meant many coupe-cabriolets suffered from an ungainly boot which stuck out like a Victorian bustle (remember the Peugeot 207 C+C?).

But advances in roof kinematics has made it possible to squeeze a roof into a smaller area by folding it into more panels and stacking them more tightly. As a result, the 3-Series has kept its good looks.

With the roof in place, the boot has space for 350 litres of luggage, decreasing to 210 litres when the panels are stowed. Roof down it’s hard to get at your luggage (although BMW plans a new range of slimline luggage cases to avoid this problem).

You can, of course, just stow your bags on the back seat or fold them flat to gain an extra 160 litres.

The passenger compartment is finished to BMW’s usual high standard. The entire cockpit is biased towards the driver with all essential controls within easy reach.

The UK range comprises the entry level 320i, 325i, 330i plus the pick of the range 330d and the hyper-sports M3 model.