Airships have never quite taken off as a means of transport. Somehow planes got the better of them, and anyway they kept crashing.
But we're more eco-conscious than we were in the days of the famous blimps: the Hindenburg, or the R101. Could the airship provide a low-energy means of carrying freight around the world?
Former chief scientific advisor to the government Sir David King discusses why he believes airships could be used for transporting cargo in a more environmentally efficient way.