IMAGINE a city in which the streets are empty; where no children play in the parks; shops are boarded up; and where the only signs of life are black cars cruising up and down, occasionally disgorging ghost-like figures often wearing black veils.

Welcome to the land called PCL. Prime Central London.

We are talking here of the key inner-London boroughs of Knightsbridge West End, Kensington and Chelsea and Holland Park, where the average price of a house is now £1.53m. That is not a misprint. A relatively humble flat in central London will cost you as much as a castle in the Highlands. House prices have risen there by £100,000 this year alone, and are so high even the estate agents are complaining about them.

This is because these areas are dying. Increasingly, properties in PCL are being bought as investments by non-residents, or non-doms who rarely stay there. As a result, shops are closing for lack of trade; services are grinding to a halt; street life is disappearing. Central London is becoming a plutocratic ghost town.

What has this to do with us? A lot. The former SNP leader, Gordon Wilson, went somewhat over the top this week in calling London a "cancer". And he could perhaps have chosen a better moment to call on Scots to attack this "southern cancer" than the very day the Tartan Army was heading down to the metropolis for the first Scotland-England international this century. But Mr Wilson was right in one sense: London isn't healthy; its growth is out of control; and we are all suffering the consequences.

The 10 million people within the M25 are increasingly living in a different world from the rest of us in the "provinces". Britain has become a grossly unequal country in which the top 1% of the population have seen their wealth soar over the last 30 years of low taxes and rampant property inflation. And the recession barely put a dent in it. It is a matter of simple geography, that most of those super-rich live in London.

Barclay's wealth map indicates that there are 287,000 millionaires in London compared with 40,000 in Scotland. The city has become defined by their wealth. It is a rarified economy where bankers make fortunes in the City of London and then invest it in property that increases relentlessly in value. This is not an economy of making things, but of speculation and rent. It sucks value out of the rest of the UK, through bank bail-outs and loan interest charges, denuding the provinces of investment capital.

Yet the City of London would not exist had the taxpayers of Britain not paid for the 2008 crash, and it is kept alive by quantitative easing - free money - which boosts inflation for the rest of us. In the Government's Help to Buy scheme, £130bn of public money is being thrown largely at the London property market. The beneficiaries of this welfare state for the banks seem oblivious to the debt they owe to the ordinary people of Britain.

Indeed, London hoovers up the bulk of national wealth, and then complains that it isn't getting enough back in public spending. It has long been the case that London receives more public spending per head than any other region apart from Northern Ireland. This is the case even if you exclude those "non-identifiable" but costly expenditures on infrastructure projects like Crossrail, HS2. As the Institute for Public Policy research noted in June, more money is spent per head on transport in London than in all of the other regions of the UK combined.

But you wouldn't believe it to hear city's political representatives. "London is not a cash cow for the rest of the UK" declared Boris Johnson, London's tousled tribune, recently. The London Mayor never tires of celebrating the city's many achieve­ments. Like London's Olympics - not "Britain's", note. It's one long party at the nation's expense.

Boris Johnson's London Finance Commission has even talked about London declaring UDI from Britain, seizing its entire property tax base and using it to pile up revenue. The M25 zone would become a kind of international tax haven, run by and for bankers.

A columnist with a London newspaper in May called for a separate currency for London, against which the "rest-of-Britain pound" would be devalued. He called on London to leave the European Union to protect its financial services sector to avoid European bank regulation. "The rest of Britain", he argued, "may have reasons for wanting to stay in Europe, but it's time for London to get out."

As an encapsulation of metropolitan arrogance, this takes some beating. However, London really doesn't need to leave the UK. It has captured the UK Government, Whitehall, the Bank of England the BBC and most cultural organisations. The rest of the UK needs to restore the balance.

The London financial establishment was responsible, through its greed and irresponsibility, for a financial crash that has impoverished many of Britain's citizens and made us all - outside London - poorer. But cocooned in their media bubble, and intoxicated by house prices, few in London's elite seem to care what happens outside the M25.

Many Londoners no longer regard themselves as citizens of Britain, but as citizens of the world. They move between international capital cities and expensive playgrounds, and have no real concept of the nation state and its social obligations.

And this matters for the fate of the United Kingdom. London was not always an insular city state. In the decades after the Second World War, Britain meant something, and the capital city recognised its debt to the other regions. The state saw inequalities of wealth between regions as destabilising and sought to counter them by regional policy. Not any more.

Lord Heseltine's report last year, No Stone Unturned, calling for public investment in local enterprise partnerships outside London was the last gasp of regional policy. He argued that London was too big, too powerful and too myopic. It was ignored by Ministers - not rejected, just left to gather dust.

Yet the south-east of England is becoming one of the most congested regions on earth. It is environmentally damaging and economically inefficient to concentrate economic activity in one corner of the country. People have to travel long distances to work, paying excessive rail fares. Young people have great difficulty putting a roof over their heads. Infrastructure costs become excessive and small enterprises find they cannot survive.

The Scottish Parliament has begun, in a small way, to pull economic activity north through the promotion of green energy and life sciences. But the work has barely begun. There is a real danger that a No in the Scottish independence referendum next year will bring it to a dead stop.

London is accelerating away from the UK, as the recession fades, and it may take a negative referendum result as a sign that it doesn't need to look in the rear mirror. It will be up to all parties in Scotland to ensure that whatever the outcome, Scotland does not revert to what it became in the last century: a tartan theme park for the southern upper classes.