I hold no brief for constitutional monarchy. It has been observed that constitutional monarchies tend to work better than republics, but to the extent that is true, I would put it down to the presence of a constitutional monarch being an indication that other undemocratic elements are also present — in effect, that the regime is an "old democracy" rather than the inferior, more-democratic "young democracy". The actual monarchy itself has no significance.
There are nonetheless reasons for welcoming the continuation of the line of the Hanoverian usurpers. First, they serve to distract democratic idealists. The centres of real undemocratic power suffer less opposition because purists allow themselves to be drawn into endless pointless arguments about the trivial cost of the Monarchy versus the sentimental value of tradition and the tangible value of the tourism industry. (Back when I believed in democracy, I eschewed republicanism for precisely that reason).
Second, the Royal Family is a contingency plan of sorts. If we are ever to escape slow strangulation by Old Democracy, then an assumption of power by the monarch is about the least unlikely mechanism. The crisis that would lead to such a change would have to be extreme, but it is only very unlikely, not unthinkable.
For instance, there is evidence of some planning of a military coup against Harold Wilson, which it is claimed would have installed Lord Mountbatten as interim prime minister. Mountbatten would have been a logical choice from one point of view, as a member of the Royal Family, a World War II General, and a former ruler (of India). It came to nothing, but there could be a next time, and a King ready to take over ultimate authority would be a large asset to such a conspiracy — particularly as we are a bit short of famous generals or colonial governors. On the other hand, it would be plainly impossible in anything resembling current circumstances, because the USA would not permit it. For any future crisis to produce an escape from democracy, the US would have to be substantially weakened or would have to move first. (The story is that CIA at least were backing the Mountbatten plot).
That story (assuming for the moment it is true) does bring home the danger of any attempt to move to non-political government. Really, Mountbatten? I am reminded that I do not support the idea of a royalist coup in the same way as a democrat supports his party to win the next election. My thought is more that if it did somehow come off well, it would be a good thing. Things would have to get a great deal worse than they are for it to be worth that kind of a risk.
The difficulty is that while the benefits of abolishing politics are real, they cannot be felt for at least a generation: the first ruling Monarch will not have inherited only his crown, not his power, and will have to work as hard to hold it as any other dictator. Charles II nearly pulled it off, and if he had a son rather than his plonker of a brother his efforts might well have been enough. But it is much easier to mess up than to get right.
So, for those thin reasons, I am celebrating the prospect of the continuation of the House of Windsor into the future. Gawd Bless 'em
Speaking of which, I think I may have resolved what I felt was a problem with my political position. I am an atheist who believes in the Divine Right of Kings. There is some hint of a logical inconsistency there. But in fact the two beliefs go together. The concrete premise of my position is that competition for power is more damaging than power misused. Therefore I want no decision to be made about who has power — since any decision will cause competition. What better way to avoid a decision than to put the deciding power into hands that do not exist? God says the King shall rule. If you disagree, do not appeal to the army, the mob, the United Nations or the electorate — take it up with God. In the meantime, the King shall rule. God save the King!
There is one detail of the Royal engagement which might be significant: the princess-to-be is a commoner — one whose parents had, at one time, to work for a living (gasp!). This is contrary to tradition — is it a problem?
The biggest danger is that by choosing a bride from within the realm, the Royal Family is opening up a competition for power among rival interests. In the long run, a monarchy where the heir to the throne tended to choose his bride from his student colleagues (rather than from a predetermined small selection of princesses) might produce hugely destructive competition between political factions to get their daughters into the right courses of the right universities. Factions would seek to control university admissions departments, influence the Royal youths' choice of courses, possibly causing huge damage to academia in the process. That perhaps sounds far-fetched, but in fact compared to the steps taken by lobbies and interest groups today to gain indirect influence over policy, it's quite minor. Minor it may be, but it's not what we want.
(For an analogous line of reasoning, see my speculation about celebrities entering politics. The root issue is the same — if some activity becomes, in addition to its original purpose, a route to power, then in time it will become nothing but a route to power, and whatever useful purposes it had will be lost).
The commoner issue, then, is potentially a bad precedent in the long run. In the current circumstances, I don't think it's worth worrying about at all. Since, for any of the above to matter at all, we first have to take the giant, improbable step from constitutional monarchy to absolute monarchy, anything that makes that step slightly less difficult is worth considerable sacrifice. Attempting to find a suitable European princess is not something we need to be spending effort on.
So, here's to William and Kate.