Time was that folks would buy their way out of Hell with indulgences. History does not record whether the buyers would then show off interminably about their new-bought righteousness, but I bet they did.

A similar thing is happening today with organic, locally sourced food. Conscience becomes smugness as ethically minded folks cannot forbear from telling you exactly how local their carrots are. How British, they trill, is our beef. Behold the green, green beans of the Home Counties.

This smirking confidence in their ethical correctness is not only unbearable but wrongheaded. You can’t buy your way out of Hell with indulgences and you can’t save the planet by spending £3 on a cabbage.

The boring fact is that the rustic simplicity of buying local does not necessarily equal ethical correctness. When consumers make almost any purchase, they engage with complex economics and politics and if they wish to analyse them ethically, they will find that they have to think harder than they anticipated.

Take this dilemma. The organic farmers of East Africa may be denied Soil Association accreditation because of concerns over the food miles entailed in transporting their produce to Britain. Many of them are desperately poor and face becoming poorer if they are unable to sell to the West.

Perhaps the consumer may decide that concern for the environment overrides concern for the world’s farming poor. Noble indeed. But it is all the energy expended in the production of food, not just in air transport, that determines the true carbon footprint. When one considers that New Zealand sheep are farmed in a less energy-intense environment than British ones, the carbon hoofprint of the little lambs is less easily quantifiable.

Organic food may have bad environmental effects as well as good ones. In the absence of pesticides and herbicides, farmers have to rely on crop rotation to maintain production levels. Because of the need to leave land fallow some years, substantially more land is required for farming. As organic farming becomes more profitable and widespread, deforestation could threaten.

I could go on. Is it really best for one person to drive his or her car to buy local goods from the butcher, the baker and the Cath Kidston tablecloth-maker? Perhaps the supermarkets are greener because they pack thousands of things into one lorry and customers only have to make our trip to pick up all their goods. How many people trouble to wonder whether supporting British food producers is actually thinly disguised and economically damaging protectionism?

There are no easy answers to these questions, but if British consumers hold off handing over the cash for long enough to engage the brain, they will find a glut of hard-to-swallow food for thought.

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