BMW has unveiled its Zagato roadster concept at the Pebble Beach Concours d'Elegance in the United States.

It is based on the BMW Z4 35iS, but the bodywork is more of a classical roadster than the sharp-edged Z4.

"This car is not designed only as an elegant convertible, but also as a masculine and extremely dynamic sports car which evokes a powerful driving experience," says Zagato chief designer Norihiko Harada, describing the design philosophy behind the BMW Zagato Roadster.

Zagato, founded in 1919, is the only automotive body manufacturer still in independent ownership. Founder Ugo Zagato learned his trade in – among other industries – aviation, where aerodynamics and lightweight construction play a central role. The "necessary beauty" of aerodynamics and lightweight construction came to represent a maxim of design and led to classics such as the Aston Martin DB4 GT Zagato, now one of the most valuable cars in the world.

There are rumours that the BMW Zagato Roadster could go into very limited production, but the price would have to be very high indeed. The BMW Z4 35iS costs £45,350 and you can probably double that for such a low-volume car as the Zagato. The Zagato gets the advantage of a power upgrade from 335 bhp to 400 bhp, but that would be an awful lot of money for what is essentially a rebodied mid-market BMW convertible.