Republicans are right that it could be replaced in its constitutional role at the stroke of a pen and nobody would notice. But the chosen replacement, no matter how nationally heroic or admired he or she had been, could never give us a line of succession. Heirs to a throne multiply its value, as William and little George are demonstrating.
The essential virtue of royalty is the element that opponents most hate, hereditary selection. It gives us a person for life. We look at that baby and know that whatever happens, whatever he may do, we or our children and their children will know about it.
For better or worse, his life will be a common reference point, through time and around the world. That can be said only about Britain's monarchy, no other is known so widely. Not much more than 100 years ago the United Kingdom's royal line was just one of several of similar status in Europe. In fact, Britain had adopted Dutch and German dynasties at times.
Quite how these descendants of Queen Victoria have managed to maintain their singular status in the world is a study in itself. It probably has much to do with the result of the world wars of the 20th Century, which began 100 years ago this year.
Defeated Germany, Italy, Austria, and effectively defeated Russia, all became republics. Royal families in countries that were invaded or dominated by Germany in the second war have survived but the world is hardly aware of them.
Whatever the reason for the global celebrity of Britain's royal house, we are very fortunate to be a part of it.
My enthusiasm for the monarchy has waxed and waned with the performance of the Queen and Prince Charles. Both, I think, could have shown more interest in this country at important times. But it is a long time since I felt a need to sever the link for the sake of national pride.
The idea that we need to ditch the monarchy to prove our independence is adolescent.
Today's younger generation seems more mature in this respect than mine was, maybe because William and Catherine are of their generation.
This young couple are easily the best royal visitors we have seen. They look and act like their contemporaries, which the young Prince Charles never did. Diana was different, too much younger than him, too unsure of herself to begin with and too conscious of the camera later.
Catherine looks natural, comfortable and perfectly sensible in her roles as a public woman, partner, mother and fashion plate. You can see it is not destabilising her. She is not afraid to smile as anyone would at first sight of a ceremonial bare bum.
William has been here so often - coming at important times such as the services for Christchurch and Pike River - that he has more than made up for the family's previous failings in my book.
The way both of them were engaging, and encouraging their baby to engage, with the families at the Plunket event in Government House appeared effortless. It was also a lesson for me of royalty's social power.
Plunket's guests included a gay male couple with a baby. I wrote a couple of hard columns last year questioning the wisdom of legislation that would sanction the placing of children in the care of two men. I was wrong, those two guys and their child looked fine.
Had the guests of honour been less than royal, I doubt news media would have acceded to Plunket's request not to highlight the inclusion of the male couple. In fact if the guests had been any other royals, media might not have complied. These two inspire high standards.
What a pity, momentarily, that David Cunliffe should lower the tone. His bleat about the Prime Minister's appointments with them, two more than his, was graceless and pathetic.
John Key, meanwhile, needs to remind me why he wants to change the flag.
