There's a drought in most of England but plenty of water elsewhere. Why not move it? Yes, water is heavy, but it's also slippery and moves down hill. Tom Heap investigates why water companies seem so reluctant to trade with each other. Some suggest it's because they make their profits by pouring concrete in their own patch, rather than by doing deals with their neighbours. Others think it's because they don't pay a realistic price for the water they take out of rivers in the first place. So are the problems of water shortage as much to do with the economics of the industry as with the lack of rain?

Producer: Jolyon Jenkins.