WHEN the French government decided to bring in new number plates, it all seemed simple. Under the old system, car-owners had to change their plates every time they moved from one département to another. Under the new rules, which came into effect last year, a licence plate belongs to the car even if the owner changes address. As a logical consequence, new plates would no longer display département numbers.

Yet this was to underestimate the fierce attachment of the French to their départements, first created after the 1789 revolution. Under the first version of the new plan, the département number was to have been an optional add-on. One argument, never quite made explicit, was that this would enable drivers to avoid stigmatisation. Those from certain rough banlieues, such as Seine-Saint-Denis, north of Paris (93), have always been treated with extra suspicion by the police. They could now choose to be less identifiable on the road.

The French were dismayed. One poll found that 71% disapproved of the numbers becoming optional. Some feared that it might be the beginning of the end of the administrative département. Families argued that it would ruin car games for children. Over 220 parliamentary deputies and senators joined a campaign, “never without my département”, demanding the numbers' reinstatement. “It's a matter of roots, of attachment to a land,” said Richard Mallié, a deputy from Bouches-du-Rhône (13), who led the campaign.

Eventually the government backed down and agreed to make département numbers compulsory again—but in tiny, almost illegible characters. The result is an overloaded ugly mess. Worse, the département number is now pure whimsy: car-owners can choose anywhere they want, not just where they live. And they can change without modifying their official registration.

A year after the new licence plates were introduced, who wants to parade their roots, and who to disguise them? The most popular choices seem to be the 69 of Rhône, around Lyon, and the 59 of the Nord, centred on Lille, a département mythologised in “Bienvenue chez les Ch'tis”, a warm-hearted 2008 box-office hit. And the least sought-after? Not the 93 of Seine-Saint-Denis, but the 75 of Paris and the 92 of Hauts-de-Seine, which includes the swanky suburb of Neuilly. Parisians, the car dealers say, turn out to be the ones who are keenest to hide their origins—perhaps to protect their cars from casual vandalism when motoring on holiday, prompted by their reputation for haughty arrogance.