Boris Johnson wants us to grow our own vegetables

Imported food is so pre-crisis; local produce is the thing — even, improbably, in London. Allotments are cropping up all over the city.

Downing Street and Buckingham Palace both have one. Boris wants us to get down and dirty in the vegetable patch: his "food champion", Rosie Boycott, is encouraging us to grow potatoes on our roofs (yes, really). Now it's going national. Hilary Benn, the Environment Secretary, wants a "radical rethink" of the way Britain consumes and produces food.

And last month the Government's Sustainable Development Commission argued for "maximum and appropriate sustainable food production in line with the proposed new definition of sustainable food security". I'm not entirely sure what that means, but a cursory reading of its report implies that it believes we need to dig for victory now, just as we did 70 years ago.

I have no problem with vegetable-growing as a hobby. Many of us, when we have finished toiling away at our computers, indulge in a bit of composting to satisfy our inner peasant. I'm sure Gordon Brown likes nothing more than mulching his vegetable patch; the Queen, for all I know, may be an ardent muck-spreader. But the idea that we should be aiming for self-sufficiency at a national level seems to me both daft and dangerous.

We import food for the same reason that we import plastic toys and washing machines. Other countries produce these things more cheaply and better. If we are to go back to growing our own stuff on a large scale we will either have monstrously high food bills or get paid the sort of wages that agricultural labourers get in the countries we import food from. Neither option sounds attractive.

It wouldn't benefit our health any more than it would our wallets. Stomach cancer levels have fallen in this country over the past 30 years, probably because of the increasing amount of fresh fruit we're eating. Most of that is imported. Self-sufficiency would mean going back to winters of turnips and swedes, when tangerines were such a treat that children got them in their Christmas stockings.

Nor would increasing our own food production help the rest of the world. Poor countries depend on selling food to the rich world. Already the wasteful subsidies and tariffs America and Europe have in place for protecting rich-world farmers impoverish developing countries by depriving them of markets. Any attempts to distort the world trading system further to encourage more domestic food production will compound that wickedness.

But, in the end, won't we be more secure if we grow our own food? No, we won't. A world in which people hid suspiciously behind their borders growing and making their own stuff would be a much more dangerous place. The planet will be far safer if we continue to trade with each other, and therefore have an interest in each other's security. Self-sufficiency may be useful for surviving wars, but a healthy world trading system is a better way of avoiding them.

Cath Kidston's A-grade success story

At the least academic of the many schools I went to, there was a girl who was nice, pretty and good at art but by no stretch academic. She was called Cath Kidston. Her company, which makes floral-print textiles, has just reported a 50 per cent increase in profits, to £3.6 million, on sales of £31 million.

Her success should bring comfort to the teenagers dreading the A-level results that will drop onto their doormats next week. Those marks are pretty unlikely to have much bearing on how they get on in life. A sense of style and a head for business have brought Cath Kidston more success than a barrel-load of A grades could.

A fun day for all the family

Instant solution to bored children: flying trapeze lessons in Battersea Park. The instructors strap them into harnesses, take them to the top of a 30ft tower (with net), and persuade them to grab the trapeze and jump.

The pleasure, for you, lies in watching their expressions change from terror to delight. Unless you're a lot braver than me, don't dream of trying it yourself.

Hackney's being too heavy-handed

There is evil abroad in Hackney. A friend parked her car on a single yellow line after 6.30pm and returned to find it had been towed away.

There was a notice warning of restrictions on parking in a bay nearby, but it didn't make it clear that they applied to the yellow line as well. Getting to the car pound and liberating her car cost her £344.

A quick online search shows that this has happened to many people in this blighted borough. The point of parking regulations is to discourage people from parking in particular places at particular times. If they are applied unfairly, unclearly and arbitrarily, they won't achieve that.

Emma Duncan is deputy editor of The Economist