Bono law: You go on a head

When is a hat not a hat? When it's an iconic-ironic sartorial manifestation of your personal and artistic philosophy. This, at any rate, is Bono's explication for the significance of his Stetson, which he's trying to wrest back from U2's erstwhile stylist Lola Cashman in an ongoing court case. According to his testimony, it was this headgear, rather than any amount of keening vocals and guitar arpeggios, that propelled the group into the enormo-dome stratosphere.

"I dressed like Nana Mouskouri before," confessed Bono. "She [Cashman] had a very good eye, and I'd already had the idea of making the Stetson a trademark. It's an American icon and it was part of my idea of how I wanted to present myself to the world in an ironic sense. Plus I thought it could be archived in the future." It seems a crushing amount of cultural weight - part-semiotic determinant, part holy relic - for a high-crowned, wide-brimmed accessory to bear.

But Stetsongate is just the latest flashpoint in the vexed history of male millinery. Since the hat lost its status as the exemplar of worker-drone conformity it's been reincarnated as its swinging opposite. "These days, any man wearing a hat is perceived to be making some kind of fashion statement," says the milliner Stephen Jones. "It's become a way of standing out from the crowd. Even the closest thing men have to a utilitarian hat - the baseball cap - is a way of advertising affiliations."

No one knows this socio-cultural-stylistic minefield better than William Hague. His decision to wear a Hague-branded baseball cap to the Notting Hill Carnival was, commentators agreed, the chief reason for his tenure as Tory leader being short-lived. His attempt to be "down" with the kids was ridiculed.

Hague made an elemental mistake, according to Jeremy Hackett, founder of the eponymous blue-chip outfitting chain. "A hat cannot simply confer cool," he counsels, "though it can certainly top off pre-existing personality traits." He cites the trilby and its adoption by iconoclasts as disparate as Kenneth Clarke and Pete Doherty.

Badly Drawn Boy's battered beanie serves, says the Cavalier Daily website, "to reinforce the apathetic/tortured singer-songwriter archetype co-opted from Elliott Smith, and to legitimise him to the espresso hipsters".

Hats can be used to subversive ends. The top hat was a looming status symbol, a sign its bearer had risen through the public school ranks to become a staid burgher in histrade. Now it's been reclaimed either as would-be social satire (the late Screaming Lord Sutch fought 40 elections in his) or dissolute fancy dress.

Slade's Noddy Holder was wont to épater le bourgeois (or, at least, the bourgeois who regularly watched Top of the Pops in the 1970s) by covering his topper with dazzling mirror shards.

Certainly, most men would rather go hatless than have to ponder all the Bono-esque sub-textual signals they could be sending out by donning a deerstalker. That is, unless they're as simple a soul as Jay Kay, who "just likes wearing hats, to cover my, like, greasy hair", and whose more outré offerings got him nicknamed "the prat in the hat".

Or unless, that is, they're wearing a hat for the most prosaic reason of all. If Bono had peered out from under his Stetson brim, he'd have seen that, right alongside him, The Edge was sporting his own headgear. And it wasn't because he was in the midst of a 10-gallon cultural studies seminar. It was because he was going ever so slightly bald.