If things continue as they are and Britain's Prince Charles succeeds his mother to reign as king until his death at a ripe old age, then sometime around 2040 the young couple getting married in Westminster Abbey on Friday will be King William V and Queen Catherine. By sheer accident of birth, William will then be the head of state of whatever is left of today's United Kingdom. Would that be all right? My answer is: In theory, no; in practice, probably yes.
If William and Kate behave themselves, unlike some of the gamier members of Britain's royal family, and contribute to the development of a modernized, slimmed-down constitutional monarchy, this can actually be better than the likely alternatives. As I look across Europe, I don't think countries such as Sweden, Holland, Denmark and Spain, all of which have monarchs, are worse off than those that have party politicians directly or indirectly elected to be president. Or would you rather have Buckingham Palace occupied by a President Tony Blair?
With one brief interlude in the 17th century, when English revolutionaries experimented with decapitating one of them, there have been kings and queens for more than 1,000 years. That is an amazing thing. It is the stuff of poetry. Imagine Shakespeare purged of all references to kingship. Before you abandon 1,000 years of poetry, you should be very certain that you will fare better in prose.
As we see again with the world media invasion of London for this week's royal wedding, this history, legend and mystique is also a significant contributor to Britain's soft power (the power to attract) and its earnings from tourism. I don't think anyone goes to Berlin to watch them changing guard at Bellevue Palace, or to catch a glimpse of President and Frau Wulff, and the little Wulffs. "President who?" is what most of the world would ask, if reference were made to the current head of state of Europe's most powerful country.
That's OK, if you make lots of BMWs, Mercedeses and machine tools to export to China. Britain doesn't. Instead, it has the queen, and William and Kate.
These arguments from history, poetry and soft power would have to yield if a constitutional monarchy seriously distorted the democratic process, made impossible an open society with life chances for all, and held the country back in a stuffy past of hierarchy and privilege.
In theory, it does all those things. These are among the reasons the British newspaper the Guardian has declared itself for a republic, and why many Guardian readers — though not, as a recent Guardian poll revealed, most Brits — would favor abolition of the monarchy.
In practice, however, I believe it does these bad things only marginally, and far less than it did 30 years ago, when Charles and Diana married. There are damagingly undemocratic elements in the British political system — above all, the unelected upper chamber of the legislature, the House of Lords — but the monarchy is not high among them. If we are talking about the power of a single unelected individual, the media mogul Rupert Murdoch is a far greater threat to British democracy than our hereditary head of state.
According to the constitutional expert Vernon Bogdanor, no British monarch has refused his or her assent to legislation since 1707. Some undemocratic obscurantism still results from "Crown prerogative," and the constitutional doctrine that sovereignty resides in "the Crown in Parliament," but the lawyer Richard Gordon has shown how Britain could have a thoroughly modern written constitution, firmly based on popular sovereignty, and still keep a hereditary monarch as head of state.
Queen Elizabeth II may have some limited political influence, but there is no evidence that she has used it in a worse way than presidents do in other countries. Such presidents can sometimes lift themselves above the party political fray, as Richard von Weizsäcker did most impressively in Germany, but they will always be at least residually associated with a particular party. Somewhere in the past, these leaders will have had to do what politicians have to do in order to get to the top.
Of course, monarchs and royal consorts can get into trouble too, as Prince Bernhard of the Netherlands demonstrated when he became embroiled in the Lockheed bribery scandal. But there is less chance of that happening with monarchs, precisely because they don't have to elbow their way up the greasy pole.
Countries plagued by "cohabitation" conflicts between presidents from one party and prime ministers from another — and there are many such in Europe — must often wish they had a head of state who was genuinely neutral and a personification of national unity.
To be sure, this also means you can never have a Nelson Mandela or Vaclav Havel as your head of state. But such figures only emerge in exceptional moments. To paraphrase Bertolt Brecht: Unhappy the land that has no Mandela? Unhappy the land that has need of a Mandela. And there is at least one great example of a European monarch riding to the defense of democracy. Thirty years ago this year, King Juan Carlos of Spain played a decisive role in foiling an attempted army coup against that country's still-fragile young democracy.
As for the claim that the British monarchy cements the apex of a pyramid of class and privilege, that seems much less true than it was 30 years ago. In today's Britain, unelected bankers are more powerful than any hereditary aristocrats, soccer stars as famous as any "royal."
Kate Middleton's advance to becoming a princess shows that the barriers between the upper middle class — roughly speaking, the 7% of Brits educated at private schools, as she was — and the very top have all crumbled. The deep and worsening problem is not there, at the top, but rather in the miserable prospects of social mobility for the majority educated at state schools. This is the thing that most painfully sets Britain, and especially England, apart from other modern European monarchies, such as Sweden, which happily coexist with open, egalitarian societies. This is the true English disease.
Yet those other European examples — Sweden, Denmark, Spain, the Netherlands — show that these are not necessary features of a constitutional monarchy. If William and Kate are well advised, they will work toward being the very model of a modern European monarchy. If they don't, or if Charles and Camilla don't let them, then by 2040 — even in conservative England — the job may no longer be there for them to inherit.
Timothy Garton Ash, a contributing editor to Opinion, is professor of European studies at Oxford University, a senior fellow at the Hoover Institution and the author, most recently, of "Facts are Subversive: Political Writing from a Decade Without a Name."