David Cameron, the Conservative leader, has been attracting attention with eye-catching stunts to promote his environmental credentials. He has descended into the heart of a shrinking glacier in Norway, been filmed cycling around London and replaced his car with a low-emission hybrid. Some observers ventured to ask whether he might not have purchased an even greener model. Not to be outdone, Gordon Brown, the chancellor, has declared that fighting climate change is a "moral duty". Menzies Campbell, the leader of the Liberal Democrats, has tearfully announced that he is selling his beloved Jaguar. Everyone has accused everyone else of moral posturing, and it is hard to disagree.

Politicians are hardly alone in publicly proclaiming their green credentials. Few high-profile companies are without some kind of environmental fig-leaf, while greener-than-thou Islington dinner parties debate the most fashionable ways to save the planet.