A windfall tax on excess energy-industry profits. There's a good environmental case for it.
It has a powerful backer. And it solves the same political problem that less satisfactory rival proposals aim to address.
Roy thinks it's a political winner for Gordon Brown*.
What's wrong with the idea?
(*Fair warning: All comments along the lines of 'if Hattersley is advocating it, it's a bad idea' will be deleted instantly)