John Morrish: To peel it is to love it, as they used to say before the fat police fingered Dairylea

It was always as much a plaything as food. Getting the cheese out of the foil in one perfect piece was a vital accomplishment

Parents worry about their children's food. They did in 1950, when the Dairylea cheese triangle made its appearance. The worry then wasn't obesity: they thought their children weren't eating enough. And the cheese triangle helped.

If you recall the fare on offer, you will know why there was a problem. Children's food had not been invented. Children ate what everybody else ate, and since everybody else had just escaped from rationing, no one cared what it was like: grey meat, vegetables boiled to mush, gravy; and then semolina, tinned rice, or ice-cream. Classic British cuisine. Cheese was for sandwiches, or formed part of a dreary salad mainly composed of lettuce. There was only one variety, often referred to as mousetrap.

And then along came the cheese triangle, one of the first foods that was also a plaything. Children adored them. But now that lawyers in America have discovered obesity, manufacturers are nervous. The Dairylea cheese triangle, as such, is unknown to Americans: it's too small, for one thing, to qualify as food. Here, though, it has come under suspicion from health experts, thanks in part to Kraft's ingenuity in stretching the off-white spread further than was perhaps wise.

Take a look in the refrigerated cabinet and you will see that alongside the simple triangle you can now buy Dunkers, Strip Cheese and Slices, all carrying the Dairylea name and logo, all constructed from the same basic raw material. The particular villain is the Dairylea Lunchable, a sealed pack of processed meat, processed cheese and some crackers - which would no doubt be processed if they could be. This recently won an award from the Food Commission, a campaigning organisation. A panel of parents called it the least healthy children's food on the market.

Kraft, of course, insists that the Lunchable is an occasional treat - surprising, given its name - that wise mums will always top off with a piece of fresh fruit to create a balanced meal. Yeah, right, as the Americans say.

Things were so much simpler when food manufacturing came into its own. Quantity and economy were the goals then, accompanied where possible by basic hygiene. James Kraft, founder of the present conglomerate, invented processed cheese just before America entered the First World War. He used scraps left over from packaging hard cheese, ground it small and then mixed it with water and milk solids and some kind of emulsifying agent. The mixture was then pasteurised so it would keep.

In the Depression, it was the only cheese anyone could get: even today, the big book of American cheeses has few pages. Production of processed cheese started in Britain in 1926. But the Dairylea triangle - exhibited in the Millennium Dome as an example of British style - was Danish. It was discovered there in 1950 and imported, before its success with children led to its being made here. Since 1983, they have been made in Belgium, an unlikely enhancement to that nation's cheese-making heritage. We eat 150 million a year, despite the chemical tang, the fatty film the cheese deposits on the teeth, and the surprising aftertaste at the base of the tongue.

Getting the cheese out of the foil in one perfect piece was once a vital childhood accomplishment. Dairylea was always as much a plaything as food. You can fiddle around with the little foil triangles in the box and make shapes with them, even before you unwrap them. The box, of course, is a staple of nursery school junk modelling, making excellent wheels and turntables.

And the wedge of cheese inside the foil - part of a select class of geometrical foodstuffs, along with square crisps and tortilla chips - panders to those who think children can be made to eat by making their meals look like aircraft, fairy castles, mountain ranges, motor cars and anything other than food. There is an obvious irony here: no sooner do we stop persuading our children to eat than we start persuading them to stop.

Used safely, in accordance with the instructions, there must be many more dangerous products on the market than the Dairylea triangle. Clearly, the NHS feels the same way. An official snackbox introduced for children who had missed their main meal, and based on the best health advice, included fromage frais, fresh fruit, milkshake, chocolate bar, crisps and - a cheese triangle.