ST. ANDREWS, Scotland — On Sept. 18, just over four million voters will be asked a simple question: “Should Scotland be an independent country?” If a majority votes “yes,” unlikely but possible, one of the most successful political unions in history will break up. Great Britain will become England plus. About a third of its land mass (and many of its best golf courses) will be gone.

This will be sad — Great Britain’s greatness owes much to the Act of Union of 1707 — but by no means a tragedy. All the heated debates — about whether an independent Scotland could keep the pound sterling as its currency, whether it could join the European Union, how much of North Sea oil revenue it would receive — mask the fact that a Scotland that cut the cord with London would have a decent shot at prosperity, stability and political coherence. It would be more likely over time to resemble a Norway than not. England, once the pique subsides, would have every interest in cooperation.

One of the striking things in Scotland these days is how measured the independence campaign is. Jingoism and Scottish nationalist fervor have been forsworn. There is disgruntlement with London, and cultural alienation, but not the anger of Catalans toward Madrid. Alex Salmond, the charismatic leader of the Scottish National Party, is pitching a pound-preserving, Queen-upholding velvet divorce; not liberation from English oppression but a gradual shift to consensual independence.

There is another question that might be asked in a referendum and is not unrelated to Scotland’s restive mood: “Should London secede from Britain?”

In bubbling London, you hear talk of a first-class city attached to a second-rate country, of a money-oozing Singapore chained to Southeast Asia; and hardly a day goes by without Boris Johnson, the mayor, bleating about how the capital’s prosperity really does trickle down and is not, as one member of the cabinet suggested last year, “a giant suction machine draining life out of the rest of the country.”

That is certainly the impression much of the rest of the country has: London is an island unto itself. Economic growth in the capital was 15.4 percent between 2007 and 2012, much higher than in the rest of the country. Since the financial crisis of 2008, London real estate prices have soared; by some estimates the city’s top 10 boroughs are worth more on the property market than Wales, Scotland and Northern Ireland combined. The gap between the best and worst performing regions of the United Kingdom is the widest in the 28-member European Union. That suction sound seeping through Britannia is of the mega-projects, including Crossrail, designed to speed travel across the Greater London area, even as it languishes from, say, Manchester to Leeds.

Nowhere in Britain is the sense of a London divorced from its environs stronger than in Scotland, where the social democratic consensus (free universities for Scots unlike in fee-paying England, priority to public health, a commitment to state pensions) is strong and the alienation from the capital’s hyper-capitalism a significant theme of the referendum. The fact that David Cameron, the conservative prime minister, is a plummy-voiced, Eton-educated, upper-class Brit from central casting has played into Salmond’s hands.

Cameron’s Conservative Party is near-enough dead in Scotland, killed off by Thatcherism. The fact Blairism ended up positioning the Labour Party closer to Thatcher than to traditional social democracy left the field wide open for the Scottish National Party, which duly won a landslide victory in 2011 to take control of the Scottish Parliament and call the referendum. It is hard to resist the view that a vote for Scottish independence would give a much-needed political and cultural jolt to Londonia.

Of course, Scotland has that Parliament (created under Blair in 1999). It has a separate education system, separate churches and a separate football team. With that much autonomy, what is all the fuss about? Salmond says he wants to preserve the pound. As the recent troubled history of currency unions in Europe demonstrates, and as the governor of the Bank of England recently pointed out, such unions do not work without a degree of pooled sovereignty. If an independent Scotland wants sterling, it may have to accept a centrally controlled budget, which looks like independence-lite at best.

Given all this, and the rich history of what by any standards has been a successful union, the best outcome might be a strong independence vote that falls just short of a majority, spurring further devolution without severing the knot of 1707. And yet, gazing at the spires and towers of St. Andrews (Scotland had five universities to England’s paltry two in the 18th century), and listening to the no-nonsense good sense of the Scots, I could not help feeling that a pro-European Scotland doing its own little Scandinavia to Europe-bashing England’s London-centric neo-liberalism might be a very good thing.