There is an easy solution to Britain in Europe. Let the rest of Britain stay but let London leave. The great metropolis has never been a true partner to the other capitals of Europe. It does not walk arm in arm with Paris, Brussels, Berlin or Rome. It flirts with those with whom it does business, New York, Tokyo and Shanghai. For the rest of Britain, Europe is a commercial opportunity, a market for its goods and services. For London it is a weekend break.

The rest of Britain can sell its much-vaunted machine tools, cows and sheep, produced by free-flowing armies of Bulgarians and Romanians. Its manufacturers can trade from Harwich, Dover and Southampton to Bremen, Rotterdam and Le Havre, safe behind a Hanseatic tariff wall and Brussels lobbyists. It will do fine, and might even join the euro.

London is a different matter. Its future is global. Its two great industries, finance and leisure, are peculiar to itself. They depend on self-government, on regulatory discipline and on the value of the pound. Financial services are worldwide in application. They are clearly threatened by what Lord Lawson called “jealous European banking officials”, by regulations designed to underpin German bankers and clip London’s wings. Europe’s interest is in European bank protectionism.

The second industry is becoming equally global, that of London as a desirable place to live, a tax shelter, a luxury goods and services market. It has grown into the world’s leading centre of health and education, arts and entertainment, food and fashion. This is fuelled by handsome domestic properties, albeit under relentless pressure from luxury flats and basements.

Tomorrow a blueprint for London as a city state is to be published by the mayor’s London Finance Commission, chaired by the LSE’s Tony Travers. It proposes that the city recover its entire property tax base, comprising council tax, business tax and stamp duty. This would enable it to reorder Whitehall’s currently chaotic council tax and stamp duty banding system. The revenue would cover roughly half London’s current expenditure, and the rest could be recouped from London’s income tax, generously shared with the rest of Britain.

These are the building blocks of a non-EU London. The new city state would have a physical boundary, roughly that of the M25. Digital mapping would police the circumference, though open borders are no great problem. They exist like those between Gulf states, between Ireland and Ulster, Monaco and France.

London already has its own government under its elected “monarch”, Boris Johnson. Most continents have sovereign centres offshore, as in Singapore, Taiwan, Dubai, Bermuda. Europe has the Channel Islands. London is already an entrepot of money-laundering from Russia and the Gulf. If it needed extra cash for grand projects, it could exploit the Treasury’s “optional tax” regime by shaking down a few sheikhs and oligarchs, on pain of Belmarsh or expulsion.

There would be real distributional benefits in London’s independence from the rest of Britain. The metropolitan economy would be attuned largely to a global market in financial services, its exchange rate dependent on them. “Britain without” would see its pound devalue, thus gaining an outflow of employment and housing demand from the capital and helping its trade with the EU.

The bulk of British government would have to relocate out of the present capital. Because no one would agree on where, departments would be fragmented around the provinces, to the benefit of all. Parliament could relocate, perhaps to Salford or to an Orwellian “Elizabethville” in south Yorkshire. Essex and Sussex would concentrate development around Stansted and Gatwick, relieving pressure on Heathrow.

London is already growing ever more distant from the rest of Britain. Its income disparity is widening. It sucks resources from the Exchequer for its grand projects, the Olympics, Crossrail, HS2, museums and arts. Its property market mocks house prices elsewhere. Its schools and hospitals gobble up money. While the public sector in the rest of Britain now composes 45 per cent of output, in London it is just 35 per cent, similar to that of the US.

London is not a European city but a world city. Its real partner, indeed its civic alter ego, is New York, whose population of 8.4 million it is set to overtake. New York shares its large-scale immigration, its spread of rich and poor, its business culture, its leisure pursuits and its theatre, film and book scene. A New York restaurant menu is a facsimile of a London one. The West End and Broadway are a single performance space.

Europe has not worked as a political construct. But nor has the United Kingdom. Most of Ireland has long gone. Scotland is girding its loins to go. Wales and Northern Ireland are special cases, but are winning progressively more autonomy. One day their representation at Westminster will be diminished.

London remains. The threat to its prosperity from euro-regulation is real. Under pressure of austerity, EU cartels and trade restrictions are likely to increase, which is why David Cameron was wise to go to Washington this week to treat with Barack Obama on the subject. The commercial future of London lies in the outside world, above all with the Americas, the Far East and India.

The rest of Britain may have reasons for wanting to “stay in Europe”. It is time for London to “get out”, of both the EU and the UK. But who would dare back a referendum on that question?