EVERYTHING is “sustainable” these days: there are sustainable cars, sustainable blocks of flats, even sustainable school dinners. Everything, that is, except the Prince of Wales’s arguments. The heir to the throne said this week that if we wanted to save the planet we must all eat more local, “sustainable” food, and complained that we couldn’t go on importing food by jet aircraft. We can perhaps pass over that the Prince has a vested interest in pushing the sales of British grown organic foodstuffs such as Duchy Originals biscuits. But if 20 million people in the South East were all to try to survive on local food, the only way that sufficient calories could be produced would be by turning over even more of the countryside to intensive cultivation of sugar beet. And I don’t think that would match the Prince of Wales’s idea of “sustainable” agriculture. It certainly wouldn’t please the Government’s health police.

The concept of sustainability has been used by the environmental movement since at least the 1970s, but it acquired general currency as a result of Our Common Future, a report published in 1987 by the World Commission on Environment and Development. The commission, like a lot of worthy international initiatives on any subject other than whaling, was chaired by a Norwegian — former Prime Minister Gro Harlem Brundtland. According to the Brundtland report, sustainable — or in Norwegian baerekkraftig — development is anything “which meets the needs of the present without compromising the ability of future generations to meet their own needs” — a definition that the UN Division for Sustainable Development has adopted.

We get the idea, but how many generations do we need to consider when we fill the car with premium unleaded? There must be some limit, because otherwise it is a nonsense to talk, as the Kyoto Protocol does, of “sustainable use” of fossil fuels: no matter how far we eke them out there will come a time when a finite resource runs out. Must a “sustainable” activity be able to be continued for a hundred, a thousand or a billion years? If the latter, clearly at some point the activity will have to be transferred to another solar system, because nothing is burning its way through a finite supply of fossil fuels as greedily as the Sun.

In the absence of any precise meaning, the concept of sustainability is pointless. It could mean virtually anything, and therefore means absolutely nothing. It has become merely a marketing slogan. If you buy a “sustainable” hardwood floor does it mean that the factory could theoretically carry on sawing up trees ad infinitum, or that the floor will sustain your weight? I couldn’t argue with a consumer who was more interested in the latter assurance: at least it can be proven.

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