PITY Britain's politicians. They spend much of their time being ignored as they try to explain important issues to the public. The repetition involved can be numbing: New Labourites used to complain that the moment they became heartily sick of saying something, and convinced that they sounded like interminable bores, was about the moment ordinary people began to catch on. Just occasionally, though, people do listen to politicians. The consequences can be calamitous. So it has proved over the past couple of days. On March 28th David Cameron condemned a threatened strike by fuel tanker drivers, which could occur in about 10 days' time. As for ordinary people, he said, they should not respond to the possibility of looming shortages by queuing to buy petrol. But motorists might take the precaution of topping up their fuel tanks over the next few days. Francis Maude, the Cabinet Office minister, added that it could be sensible to keep a few extra litres of fuel in a jerry can. Telling people not to panic and rush to the nearest petrol station has been quickly followed by a panicked rush to petrol stations. Britain's newspaper websites are full of stories of lengthening queues, filling stations running out of fuel and angry customers. The Daily Mail's article is particularly detailed, as one would expect from that well-resourced outfit. The panic-buying story is leading the 24-hour news channels, and will surely be on almost all of tomorrow's front pages. This is, of course, extremely silly. Not individually silly—if there is a run on petrol it makes sense to get in the queue, just as it makes sense to pull all your money out of a bank during a bank run. But it is collectively silly. As motoring groups have pointed out, there is no overall petrol shortage; if everybody behaved normally, there would be plenty to go round, and no queues. Britons will get at least seven days' notice of a strike (if it comes) so they really do not need to be panicking now. The Guardian is directing readers to post their accounts of panic buying, and has linked to a map which indicates the silliest areas of the country. The commuter belt to the north and west of London is pretty silly, as are parts of the north-west. The south coast is silly. Scotland is not particularly silly.

Why do Britons go in for this sort of silliness? Perhaps it is memories of the 2000 fuel blockades, which caused severe petrol shortages. But the tendency to panic-buy runs deeper. A colleague reminds me that, in the 1970s, there were occasional rumours that stocks of certain foods (such as sugar) were running low. Those rumours invariably provoked panic-buying. Perhaps Britain retains a folk memory of post-war rationing.

Or perhaps it has to do with the peculiarities of Britain's media market, which is unusual in two ways. First, as is often noted, it is extremely centralised. The main five free-to-air television channels account for 56% of viewing. Unlike in, say, America, they mostly broadcast the same news reports to homes across the country. The press is almost as centralised. Last spring, the National Readership Survey reported that Britain's 11 national daily newspapers had a collective readership of 24m people (of course, some people read more than one newspaper). Reports of panic buying in one part of the country are thus efficiently transmitted to all other parts of the country.

The second peculiar thing about the British media market sounds like the opposite of the first: it has an extraordinarily well-developed social-media culture. A recent report from the Boston Consulting Group shows that Britain combines unusually high internet penetration with unusually widespread use of social media like Facebook and Twitter. Those social networks are great for amassing eye-witness reports, as well as for spreading news both genuine and phony. Newspaper and television reporters love Twitter, and increasingly use it to provide local colour for their stories.

Combine a highly centralised broadcast media with a highly developed social media, and you get an exceedingly efficient device for collecting, sifting and broadcasting bad news. Perfect for stoking something silly, like the panic-buying of fuel.

Yet the silliness of the run on petrol underlines a problem that is not silly at all. Britain's coalition government is committed to devolving power away from Westminster and towards elected mayors and police commissioners. One big objective of these reforms is to change the direction of public complaint. If something goes wrong with policing in, say, Bristol, that would be a problem for the mayor of Bristol and for the elected commissioner of Avon and Somerset Police, not for the government in Westminster.

The peculiar nature of British media means pulling off that change will be difficult. In Britain, local crises have a tendency to become national crises. A foolish statement about topping up your petrol tank uttered in Westminster is quickly communicated to the country. The resulting fuel shortage in one corner of the country is quickly communicated to the rest of the country, and becomes a national problem. David Cameron, what are you going to do about it?