New York? London? We're all on the move

Diana, Princess of Wales may or may not be planning to move abroad, but she has the choice. So, too, will more and more of us. If she does go, she will be joining a new, still-exclusive but rapidly growing community: the global citizens.

These are the people who think of themselves as international, rather than national; who can choose to live anywhere in the world; whose main base is simply a matter of convenience (and sometimes tax) and can be changed at will; and to whom countries, even medium-sized ones such as the UK, seem provincial and small.

Of course, Princess Di is also a star: she is a top-of-the-range global celeb. Royalty have in any case always been international, witness the family links between the European royal families of the last century. Countries would "out-source" their royal families from the global pool of suitable persons. But until now the possibility of being a global citizen has been limited to a tiny minority who have made, inherited or married fortunes, or have had one of those rare trades - such as writing - that can be carried out anywhere.

Now that has changed. As the cost of telecommunications has plunged and the capability has soared, anyone who works on screen can - in theory, at least - live anywhere. For the first time in history, people do not need to live in the country in which they work.

The result is that instead of there being only a tiny minority of rich people who have real freedom of location, and who can therefore think of themselves as being beyond the clutches of a nation state - perhaps a few hundred thousand, world-wide - there will be millions. It was once just the nobility; now it is the mobility.

As people become more mobile, just as companies have done, some tough questions arise. One obvious one is: how will countries continue to raise revenues when people, as well as firms, can move away? We are used to the idea of governments bribing foreign countries to set up local plants; and international competition is holding down company tax rates, as Gordon Brown acknowledged in his Budget. But we are seeing only the very early stages of this process as far as individuals are concerned. Expect to see more and more governments pitching their personal taxation at levels that are attractive to the new mobility.

Behind that, though, is a deeper set of questions. What is the glue? What will hold people to countries, hold societies together? If an increasing proportion of people are able to base themselves anywhere, what will stop choice of location becoming a mere convenience? Will loyalties become increasingly horizontal - to other people in similar occupations elsewhere in the globe, rather like the loyalties of the European royal families in the second half of the last century? Or will they remain to a large extent vertical - to their neighbours and compatriots?

There are, I think, at least two sorts of glue, both of which governments would be wise to try to strengthen. One is professional; the other is social.

People have to work somewhere, and while the telecommunications revolution will liberate many workers from the daily trek to the office, there will still be reasons why people will be limited to specific locations. One is the phenomenon of skill clusters. In theory, software writers could be anywhere; in practice they cluster in places such as Silicon Valley, for there seems to be an added dimension in the performance they achieve if they live in reasonably close proximity to each other. Anything that can be done to strengthen skill clusters (such as Bill Gates's support for boosting software skills in Cambridge) will help bolt a potentially mobile business to a particular country.

Good physical communications are also important. Paradoxically, the more people work on screen, the more they also need to be near an airport. For while their main work can be carried out anywhere, they will from time to time need to meet other people in their business - and, of course, the people who market their services.

You can even see this professional glue in the case of Princess Diana. She could live anywhere, but in practice she needs to be reasonably near the people who "market" her services: the media. (Seen in commercial terms, her problem is that she does not have control of her own distribution: a brilliant product, but one that is haphazardly and even destructively marketed.) The media will go down to St Tropez for a good story, but if she is to continue her serious work, she probably has either to remain in the UK, or, perhaps, move to the US. She would not be able to attract appropriate publicity were she to move to, say, Switzerland or Pakistan.

The other sort of glue is social: people will chose a particular location because it offers the right mix of social characteristics. Why do many rich people live in the middle of giant cities, where they pay more for space, and suffer congestion and noise, when they could objectively have a better quality of life in a medium-sized country town? Answer: because mega-cities offer social and cultural attractions which even decent-sized provincial towns cannot match. But if the disadvantages of cities become too great, and the medium-sized towns are clever in creating social and cultural events, then they can attract mobile people. If you want to revive a run-down city, make sure you build an art gallery, as well as new office blocks.

This matters for countries, too. Social and cultural events not only make them more attractive for the mobile. They also act as a glue binding different groups of people who are not potential migrants. While it is inevitable that many people will identify more with their peers in similar professions in other countries, that does not mean they will necessarily want to cut themselves off from different people within their own. Not many people would want to live in a gated community - or, rather, live in a society that makes gated communities necessary.

Britain has been extraordinarily successful in attracting people who see themselves as global citizens. That has something to do with taxation, which is favourable to non-residents, but it surely has more to do with professional clusters (as in financial services), and social and cultural attractions. This enriches the place, not just financially, but culturally, too. We should therefore worry if our own home-grown members of the new mobility feel uncomfortable here. If Princess Di is indeed thinking about moving, we should try to persuade her to stay.