The other night, my girlfriend and I were sitting on the upper deck of one of London's bright red buses, staring out the window with the drowsiness of early evening, when we came to a lurching stop. Just then, six boys clambered up onto the second deck. They all wore hooded sweatshirts. The boys moved toward the back and began, in an exuberant way, to make a ruckus—shrieking, laughing, speaking in a peculiarly adolescent patois. There wasn't menace in their adolescent singsong, exactly, but its brazenness made their message clear: We own this bus. I gripped my girlfriend's hand. We stared stiffly forward, our lips tight, hoping that whatever the boys were saying didn't concern us.

This particular scene, we later learned, is nothing new. Hoodies—youthful miscreants named for their trademark outfit, the hooded sweatshirt—have become a symbol of urban menace in London. A few days earlier, we had seen another half-dozen identically dressed boys shouting and terrorizing passengers on the Underground. To sit at London dinner tables these days is to hear vivid tales of harassment, mugging, and stalking. London's tabloids ("Grandad Dies in Hoodie Horror") treat the hoodie like Jack the Ripper; rap artists have immortalized him in ballads; politicians of all stripes have searched his unshaven mug for clues about Britain's youth culture. Though he would hardly care to know it, at this moment the hoodie seems to contain all of Britain's anxieties.

Britain, of course, has long exorcised its anxieties through its Angry Young Men. The original gangsters to bear that title were John Osborne, Philip Larkin, and Kingsley Amis, whose writing and poetry seethed with resentment; there were angry rock bands like the Rolling Stones; angry punk bands like the Sex Pistols ("All we're trying to do is destroy everything"); a second generation of brash novelists that included Ian McEwan and Martin Amis; and, not least, the benighted soccer hooligan, of whom Britain has bred a fragrant and seemingly unflagging supply.

The hoodie is an altogether different kind of yob. He is known for his "loafing loutishness, his truancy, his petty thieving, his inclination to find support and solace in the gang," as tabloid the Evening Standard put it earlier this year. Hoodies are usually in their early to late teens. They cruise dark streets and shopping malls looking to create mayhem; last May, England's largest shopping center banned the wearing of hooded sweatshirts. Hoodies accrue "ASBOS"—slang for "anti-social behavior orders"—which they flaunt as badges of their indecency. The hoodie has become symbolic of England's juvenile delinquency: Earlier this month, the BBC published the results of a survey that said that 15-year-old English boys ate dinner with their families less often than their European peers. Any guess what these boys are wearing?

The British courts are beginning to see the first wave of hoodie-related crime. Sixteen-year-old Dale Carroll of Manchester recently appeared to face charges that he (in the summation of one news service) "threatened a man with an axe, threw a firework at a cyclist, and tried to cut down a CCTV monitor with a chainsaw, while wearing a hoodie." His punishment was the revocation of his hoodie-wearing privileges. When the courts dispossessed another 14-year-old of his hoodie, his mother told the papers, "They should have locked up the little bastard to teach him a lesson. They can piss off if they think I'm buying new clothes."

One the one hand, the hoodie is an outgrowth of "chav" culture, and his rage is of a familiar, anti-authoritarian strain. A British rapper named Lady Sovereign released a song called "Hoodie," which purports to defend the hoodie but instead reduces him to a bratty teenager: "The bouncer was approaching me coz i was dressed really inappropriately/ No hood, no hats, no this, no that."

But if we take the hoodie at face value, his presence indicates a great deal of social unease. After last year's subway bombings and August's terror arrests, Londoners have an unusual fear of predators in their midst. If you conducted a survey, hoodies would probably be more or less equally distributed across the races, though one olive-skinned boy we saw on the bus left his seat, approached a girl whom he knew, and in a loud voice asked, "Where's your veil?"

A second theory of the hoodie is that it's an outgrowth of technology. Britain is the most surveilled nation on the planet: Its 60 million residents are monitored by 4 million closed-circuit television cameras. The cameras, it has been suggested, have created a fashion: The hoodie—and its frequent companion, the baseball cap—hide the faces of youth. You could read this merely as wannabe gangster fashion, similar to how American hip-hop used the hoodie in the early 1990s. Or you could infer that Britain's surveillance culture is breeding a generation that feels so constantly scrutinized, they're trying, at some basic sartorial level, to be anti-social.

A similar theory has been suggested by David Cameron, the leader of Britain's Tory Party, who in July delivered a remarkably sympathetic speech on the plight of the hoodie. As Cameron put it:

Hoodies are more defensive than offensive. They're a way to stay invisible in the street. In a dangerous environment the best thing to do is keep your head down, blend in. For some the hoodie represents all that's wrong about youth culture in Britain today. For me, adult society's response to the hoodie shows how far we are from finding the long-term answers to put things right.

Somewhere, Margaret Thatcher just fainted. (Indeed, the Labor Party, assuming the Tories' historically sniggering role, dubbed Cameron's speech "hug a hoodie.") But as the initial shock of street crime dissipates, there's a notion that the hoodie menace may have been diagnosed too broadly. A few nights after the incident on the bus, my girlfriend and I were walking home from a bar in Soho, a posh neighborhood known for its boutiques and used book stores, when three young men came up behind us, talking loudly and bearing down on us at a brisk pace. Should we run? Yell for help? We turned right at the next corner. The hoodies walked on.