The ideal king would be rather like the king in chess: the most useless piece on the board, which occupies its square simply to prevent any other piece from doing so, but which is somehow still the whole game. There is something positively sacramental about its strategic impotence. And there is something blessedly gallant about giving one’s wholehearted allegiance to some poor inbred ditherer whose chief passions are Dresden china and the history of fly-fishing, but who nonetheless, quite ex opere operato, is also the bearer of the dignity of the nation, the anointed embodiment of the genius gentis—a kind of totem or, better, mascot.
From here. Linked by Mark Horne.
This is one of the several reasons why I appreciate constitutional monarchy.
Alastair's Adversaria 
Do you think it’s a biblical model of kingship?
Yes, I think that it is a model congruent with biblical convictions in key respects. I also believe that a monarchy can serve to uphold certain realities that are given importance in Scripture to an extent that many other systems of government don’t. I don’t believe that it is a biblically illustrated or mandated model of kingship, though. It definitely isn’t the biblical model of kingship. I believe that we have significant creative freedom regarding the manner of government appropriate to each people afforded to us within the norms established by Scripture.