BMW’s first-ever folding metal roof is a huge success – it works brilliantly, giving the 3-Series Convertible the refinement and security of a coupé with all the benefits of a cabrio. And it doesn’t ruin the car’s looks, either. Space in the back is at a premium – although no better or worse than in rivals – and the price for the range-topper is a hefty £38,000. However, with a fabulous driving experience, it’s still the best convertible on the market.

It's the big 'opening day' for the new 3-Series Convertible - the moment when BMW's first-ever folding hard-top takes centre stage.

The fourth-generation model has ditched the traditional canvas hood in the search for better refinement, security and structural stiffness.

With only Volvo's C70 offering a similar arrangement in the sector, it gives the newcomer an important edge over the Audi A4 Cabriolet and Mercedes' CLK. However, the new roof isn't the sole innovation. There are special heat-reflective leather seats designed to keep the cabin cool, as well as the firm's latest twin-turbo six-cylinder petrol engine. So is the new 3-Series Convertible the best drop-top on the market?

Well, it's certainly one of the most stylish. As on the Coupé, every panel from the new nose to the A-pillar is different to the saloon. And with repro-filed bumpers, neat LED headlights - incorporating illuminated rings - and new air intakes, it's very sporty.

It's the roof that's the real star, though. Made of lightweight body-coloured steel, it echoes the new Coupé when closed. However, the rear screen's more upright angle, plus a chrome waistline, ensures that the two cars look rather different. Raising or lowering takes around 22 seconds - all done automatically at the press of a button or by optional remote control - and its graceful movement is a joy to behold. Made of three separate pieces, which all fold on top of each other, its activation is sure to draw a crowd!

With the top in place, there's lots of light, too. BMW claims the glass areas are 30 per cent bigger than on the old car, and it feels very airy. Roof down visibility is made better by the screen angle, and seating positions are optimised for the driver and passenger.

Yet while comfort is excellent for those sitting in the front, only children and small adults will have enough legroom in the rear. That folding hood mechanism also takes up a lot of luggage capacity in the boot, plus it leaves the load area with an awkward shape. Roof up, there's 350 litres of space, and once it's down that falls to a mere 210 litres.

A ski hatch means you'll get a set of golf clubs inside, and you can fold the backs of the rear seats down, too. But as with other metal-roofed CC models, the 3-Series Convertible isn't especially practical.

That's it for negatives, however, because just like its predecessors, the newcomer drives brilliantly. Strengthening of the chassis and windscreen pillars has resulted in the stiffest open-top BMW ever, and the 3-Series feels rock-solid over bumps, showing no signs of scuttle shake.

With such a solid platform, it's great fun through bends, turning in instantly, staying flat during high-speed cornering and giving excellent feel thanks to its weighty, accurate steering.

Refinement is also superb. With the roof down, buffeting is minimal due in part to a removable wind deflector. And when it's up, the extra stiffness and sound-deadening provided by the hood's multiple cloth layers ensures the Convertible is as quiet as the Coupé.

Performance from the 3.0-litre twin- turbo six-cylinder powerplant of our car was mighty, too, with huge flexibility, searing acceleration (0-60mph in less than six seconds) and a rasping engine note. The optional six-speed automatic gearbox was also very impressive, shifting smoothly and offering involvement thanks to steering wheel-mounted paddles.

All this comes at a price, though, as the new model costs around £2,000 more than before. But then significant improvements have been made and the 3-Series Convertible remains the best to drive in its class. Its place at the top seems assured.