Reading the newspapers at my holiday hideout in the Languedoc, I note with satisfaction that food waste has again been in the headlines. The Prime Minister has decried the annual chucking-out of £420 of food a year by the “average” family.

Mr Brown’s comments elicited interesting responses in the letters page of this newspaper. Several praised the thrift of an earlier era of home cooks, who always put leftover food to use. I take their point, but I must also add a cautionary word about leftovers.

For admirable reasons, using everything up can become a matter of pride and principle – even if the meals aren’t that good. Calvin Trillin, the funniest man ever to write about food, wrote of his mother: “For 30 years she served the family nothing but leftovers. The original meal has never been found.”

Needless to say, good meals can be made using leftovers. But the primary cure for food waste lies not in leftover management but in precision-buying perishable foodstuffs. This is simple in the Languedoc, where no retailer raises an eyebrow if you buy 50g of olives, two slices of ham or a single courgette. UK shoppers need to get into that habit. Precision-buying means staying focused.

With a weekly shop or a large order for delivery, precision-buying can be done by compiling a weekly meal plan. But buying fresh stuff over the counter gives control over both quality and quantity. If you have a chronic food-waste problem, change your shopping habits. Render unto the supermarkets your money for what they do best: lavatory paper, tins of beans, etc; for fresh goods, shop in person.

You can cross off each item against your precision-buying checklist. That’s the best way to ward off waste. It eliminates the need for ingenuity with leftovers. I’ll bet the cook at 10 Downing Street would approve. And maybe his boss would, too.

greenkitchen@thetimes.co.uk

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