A few years back the infatuation with all things urban was raging like a forest fire. Competition to be the first to agree with everybody else about it was causing sleep deprivation on a massive scale. Of course, there was nowhere for this obsession to go but into the slush pile of disappointment, but that never stopped anybody from riding a trend to the bitter end. So done and dusted was the obsession with having everybody live in Friends-type, New York-style loft apartments that many urbanites came to confuse reality with illusion, coming to believe that the countryside had already been cleared of landowners and farmers, in a lightning reversal of the great land enclosures of the 19th century, and was now under the control of wildlife.
Undoubtedly the most prominent leader of this messianic wing of the neourbanites was Richard Rogers, architectural adviser to the mayor of London and chairman of his own government-backed Urban Task Force. It was he who had first hit upon the theory that everybody lived in a city already so there was really nothing to argue about.
Unfortunately he was wrong. In an article in The Times published in 1997, he claimed that 'nine out of 10 Britons now live in cities, most of them communities of more than 100,000 people - this startling statistic reveals us to be predominantly urbanised'. Unhappily, it soon appeared that even if they were 'predominantly urbanised', the nine out of 10 Britons did not seem to like it very much for, in a later item in The Times published in 1999, Rogers confessed that his Urban Task Force 'had no easy answers on how to solve the urban exodus which is leaving towns and neighbourhoods desolate'.
Like the charge of the Light Brigade, Rogers never allowed sober calculations to interfere with a good myth, but others did.
In 1999 the statisticians Martin Mogridge and John Hollis calculated that an average of 90,000 persons per year were leaving Greater London, while up to 100,000 incomers were taking their places. Five years later the outgoing figure has climbed by more than 20 per cent, to an estimated 115,000 persons per year, according to the Countryside Agency.
Now the only way all these figures can be reconciled is not by massage but by the use of a different paradigm. Suppose, for instance, instead of a permanent input/ output model - which assumes a finality of decisions so that all those who leave the city never return to it, while all those who arrive in the city never depart - we assume a pattern more like a huge revolving door. This door permits the evolution of a two-speed population statistic. During daytime and evening the rotation of the door allows an 'Oxford Street-size' population to take over; during the night the absolute limit on bed spaces brings the numbers down.
This process of 'double-entry book keeping' is at once the key to the fluctuating density of population in towns and villages as well as in whole urban areas. It is a tool but it is also a lubricant, the reason why the Decennial Census lays such emphasis on including lodgers and visitors, and why airlines and theatres can deliberately overbook with impunity. It is also the reason why what was recorded as an 8 per cent increase in Greater London's population might, in fact, be no more than a 'snapshot' that cannot reflect the more generous swings of the rotating door. These swings give credence to the horrifyingly overcrowded images of Oxford Street that are otherwise apparently ignored for fear of political consequences.