William Skidelsky celebrates the venerable custom of food-throwing

That most venerable of customs - pelting celebrities with food - lives on

I have been thinking a lot about eggs recently. Not in the culinary sense (although, thanks to the first series of Delia's How to Cook being repeated on BBC2, the question of how to boil an egg has not been entirely absent from my thoughts), but in the pelting sense. A couple of celebrities have been splattered most satisfyingly in the past fortnight. First, Arnold Schwarzenegger, on the campaign trail in California, took one in the neck while wading through a crowd of students. (The picture of Arnie's minder, available at www.ananova.com, anxiously wiping the offending item from his cream jacket while the big man does his best to appear unruffled, is well worth checking out.) And then there's David Blaine, the American magician-cum-performance artist, who is keeping a 44-day vigil in a plastic box suspended 40 feet above the Thames, next to Tower Bridge in London. During the first week, he was assaulted with a range of missiles, including eggs, golf balls, kebabs and the sight of teenage girls baring their breasts.

Whenever I read about a celebrity being pelted with food, part of me feels relieved that this most venerable of customs has not been entirely abandoned. For centuries, throwing food was an effective means for the public to register its dissatisfaction. On the Elizabethan stage, actors who met with the crowd's disapproval would be pelted with tomatoes; the same was true of music-hall entertainers in Victorian times. It is only comparatively recently, in fact, that the expectation has come about that audiences should sit tight for the duration of a performance, before displaying their gratitude with polite applause.

But why should we be so respectful of those who entertain us? Part of the drama of a performance lies - or should lie - in the uncertainty surrounding the audience's reaction. Will the performers be feted and flattered, or heckled and abused? As anyone who has ever performed knows, being feted by an audience is a wonderful feeling. But the achievement is all the more impressive if one has also courted the possibility of being booed off stage. In times gone by, performers understood this - and were prepared to run the risk of being pelted. In today's tepid environment, by contrast, practically the only medium where heckling is acceptable is stand-up comedy.

Food-throwing must have carried a particular force in times when food was less plentiful than today. By choosing to throw - rather than eat - an item, one was in effect saying: "Your performance is so offensive to me that, rather than using this perfectly good tomato to feed my family, I am going to chuck it at you instead." Sensible cultures recognise that humans have a basic urge to chuck things, and accordingly devote holidays and festivals to satisfying that impulse. In the Spanish town of Bunol, for example, at the annual Tomatina festival, residents pelt each other with 150,000 tonnes of tomatoes; in Thailand, the festival of Songkran is essentially an excuse for a national water fight; and Hindus mark Holi by splattering each other with water and powdered paint.

Still, I am prepared to feel some sympathy for anyone who gets splattered with an egg, because I know what it's like. A couple of years ago, I lived for a while in Tufnell Park, north-west London, on a road adjacent to a housing estate. The children who lived there seemed to spend much of their time pelting passers-by with eggs. Their accuracy was uncanny; in many cases, a single shot was all they required to hit their target. This happened so often that I began to get paranoid. Were the kids singling me out?

Then, in a local shop one day, I saw a group of children making off with several boxes of eggs. When I quizzed the owner about it, he merely shrugged his shoulders. "They only want them so they can throw them at people," he said. While one side of me felt justifiable anger towards the kids for making my walk to the supermarket such a hazardous undertaking, another part of me couldn't help feeling a little jealous. For in truth, the children were doing nothing more terrible than obeying an ancient imperative - the urge to chuck.