Urban consumers have long seen farmers as a bunch of over-subsidised whingers so the distressing arithmetic of the British dairy industry is largely lost on them.

First there is the fact that 1,000 dairy farms are going bust each year while a follow-up figure shows the trend is actually accelerating. Between October and November last year, 111 dairy farmers went out of business.

Secondly, there was the tidy sum of £270m per annum - the amount that dairy farmers calculate as the gap between what they are paid for their milk and how much it actually costs them to produce it.

If you find that statistic hard to get your head around, it's the difference between the average 17.5p farmers get per litre and the 21p they need to make a living without lying in bed at night worrying about the bank foreclosing.

But every now and then a killer statistic makes the townies sit up and take note.

A case in point is the prediction of Sir Stuart Hampson, the chairman of the John Lewis Partnership, that Britain could be importing milk in five years' time. Surely an unthinkable prospect for a country such as Britain with plenty of lush green grass and a long history of self-sufficiency in milk.

Speak to farmers and there is such deep despondency that they have no trouble at all imagining a British landscape without cows in the future.

Less heated commentators paint a more restrained but still worrying scenario where our milk production contracts by 50%. This would leave enough to satisfy demand for

liquid milk but not enough for dairy products.

That would mean the yogurt in the nation's shopping basket coming from Germany, Denmark or the Netherlands while the cheese will come from Ireland or France.

The villains here are the supermarkets who cream off fat profits on the back of farmers - a cool 15p a litre or thereabouts.

Certain chains, when challenged, have done the right thing. Waitrose pays dairy farmers 3p a litre over the market rate and Marks & Spencer pays 2.5p. Other chains must be embarrassed into doing the same. Otherwise what happens to Britain's future food security? What will we do when the oil runs out and imports are no longer feasible? We won't be able to turn to our dairy farms. They simply won't be there.