It's becoming increasingly common to start a BMW news story with a reference to how the company continues to fill every conceivable niche in the market. This is no different, with today's revealing of the first details for BMW's new 1 Series Convertible.

Needless to say, the new open-topped car is based on the 1 Series Coupé, which made its debut at the Frankfurt Show only last month. The Convertible shares all of its styling cues with the Coupé, including the distinctive short three-box shape when the roof is raised. Unlike the 3 Series Convertible, BMW has stuck with a cloth roof for the 1 Series.

Packaging a larger folding hardtop into the smaller frame of the 1 Series could have completely removed any usable boot space or rear leg room. As it is, the stowed roof robs the boot of 45 litres, but with it up, it holds nearly as much as the 1 Series hatch, at 305 litres.

Odds are that buyers of the 1 Series Convertible will be more interested in the car's styling and with the roof down, BMW has managed to retain a flat rear deck. It looks better proportioned than either the three- or five-door hatchbacks.

An extensive line-up of engines will be available from launch, including 118i, 120i, 125i and a single 120d diesel. The 135i model sits at the top of the range, packing the 302bhp twin-turbo six-cylinder engine found elsewhere in the range, and also fitted with a unique styling kit to ensure it stands apart.

Prices have not been announced as yet, nor has an on-sale date.