Republicans are, or ought to be, against the monarchy on principle. The extravagant lifestyle of the royal family and the louche behaviour of wastrel princelings prejudice the public against the House of Windsor. But the only important argument concerns blood and birth. It is neither right nor reasonable that, at the beginning of the 21st century, heredity should determine who becomes the head of state. Elizabeth the Circumspect is as much an anachronism as her uncle Edward the Irresponsible would be today. There was a time when monarchists held the mirror image of that view. The case for the crown was, they insisted, unrelated to the character and conduct of the king or queen or the cost of the court. We used to be told that the monarch herself believed that she was the Lord's Anointed and that, orb and sceptre in hand, she had accepted God's invitation long to reign over us. A queen who imagines that she is personally ordained by the Almighty does not bother about the cost of an occasional journey by royal train.  If the Queen still holds that view - rather than the suspicion that she occupies the throne on sufferance - she should tell Alan Reid, the keeper of the privy purse, about it. When the cost of the royal household was revealed last week, he defended an annual expenditure of more than 36m in language that would have been entirely appropriate to a Subaru salesman confronting a sceptical customer.  "We believe this represents a value-for-money monarchy. We are not looking to provide the cheapest monarchy. We are looking at one of good value and good quality." Delete "monarchy", insert "motorcar" and the explanation could easily have been expressed on the forecourt of a suburban showroom. If this is the case for the monarchy, we are entitled to ask how many miles there are on the Queen's clock and if she is still in full working order.   It is easy to argue that an expenditure of 3m a month does not amount to a "cost-effective" head of state. An elected president - without a family to support in the manner to which the Duke of York has grown accustomed - would certainly cost less. But the important aspect of the dubious claim is its lese-majesty, not its accuracy. Once the monarchy feels it necessary to justify its existence in prosaic terms, the argument for monarchy collapses.  The superstition, on which the theory of hereditary succession is based, insists that the royal family is different from the rest of us. No sensible person argues that the Prince of Wales should ascend to the throne because he is an expert onarchitecture, education or   any of the other subjects about which he pontificates. Indeed, it is usually accepted that his opinions are embarrassingly silly. They are reprinted for exactly the same reason that it is assumed that one day he will be king. He is said to have inherent qualities that set him apart from his future subjects. It is that, not his financial prudence, which make him heir apparent.  Walter Bagehot claimed that the strength of the British monarchy lay in its ability to inspire "the feelings by which heroic kings governed their rude age" and, at the same time, experience "the feelings by which the constitutions of later Greece ruled in more refined ages". Neither of those lofty attributes encompassed the desperate desire to win the support of tabloid newspapers. Quite the opposite. Yet last week that aspiration was taken to risible extremes.  The ghost of Queen Victoria will find it difficult to believe that, after the cost of the court was published, Buckingham Palace issued a   detailed breakdown of the consumption patterns at royal garden parties. The 500,000 a year that the Queen spends on these occasions is, apparently, partly due to the gluttony of the guests - each of whom, on average, consumes 14 buns, bridge rolls and ice creams. A spokesman, demonstrating a grasp of arithmetic that is beyond question, pointed out that if the average is 14, some people ate even more. One of the ways of cutting the royal budget is, as Marie Antoinette failed to recognise, "let them eat less cake".  Even today, a monarchy can survive being hated or despised. But being the object of ridicule is lethal. However, our laughter ought to be moderated by compassion. The royal family faces an intolerable choice. Were the Queen to say - as Queen Victoria would have said - that the royal accounts were none of the common people's business, she would be excoriated for her arrogance. Yet, when she allowed her courtiers to justify the way in which she spends her money, the myth of monarchy is destroyed.  It is impossible to have a monarchy that is simultaneously regal and human. Pity their dilemma. And remember that a monarchy which is patronised with pity must, in the long run, be doomed.