I am not one of those ardent royalists who will camp out for days to see the Queen, but neither am I a rabid republican. I go back a bit and am one of a declining number who remember the last king, the Queen's father, King George VI.
If I were setting up Britain today, I would not point to one family and say, "You and your descendants shall be head of state in perpetuity". Such an idea is patently absurd and the hereditary principle contradicts the aspirations of a truly democratic society.
But, yes of course there's a but, we are where we are. We have over a thousand years of history with monarchy and although one king was beheaded that was not the end of it, but it was the beginning of a process of ensuring the people were sovereign rather than the monarch. That is the situation we are in. As head of state, the Queen sees all state papers and regularly consults with her Prime Minister, as do her representatives in other countries of which she remains monarch. This was summed up by a former UK Prime Minister, Sir John Major, who said that while no Prime Minister has to follow the Queen's wishes, with her knowledge and experience any Prime Minister should listen carefully to what she has to say. In the end, she will do as her government, elected by the people, demands of her, and this will apply to her successors.
The monarch is many things, yet none of them. Head of the Executive branch of government, head of the legislative branch, head of the judiciary (the courts operate in her name), commander in chief of the armed forces; all these yet acting as none of them. But while the monarch occupies these positions, no other person can combine them in themselves. So the argument can be made that the monarch secures the separation of powers, imperfect as it may be, which is fundamental to a democratic state. We have seen around the world how despots take on all these functions leading to dictatorship and repression, or even worse.
People often say the monarchy brings tourism and money into the UK. I think this is overstated although there may be something in it. France attracts huge numbers of tourists having been without monarchy since 1870.
It can also be argued that monarchy bestows on Britain an unrivalled amount of 'soft power'. This is hard to quantify in purely monetary terms and therefore can genuinely be regarded as priceless. Britain rates highly on any index of soft power, partly through its history, the English language and the Commonwealth. British culture is spread through the reputation of the BBC around the world, through its sporting success (most of the time!), film and music etc. Behind all this is the image that Britain projects around the world and the monarchy, especially in the long reign of Elizabeth II, has been key to this. Governments and Prime Ministers rise and fall and have varying degrees of international success, but the monarch remains, a symbol of stability, continuity and - paradoxically - of democracy.
The cost is often given as a reason for abolition but history tells us that back in Georgian times, the monarchy struck a deal with the state to surrender the income from Crown lands in exchange for a regular stipend, formerly the Civil List, now called the Sovereign Grant. Much of this money goes to running the office of the head of state and providing the various functions the monarch performs. Many of these would also be required of a President, whether titular or executive. On top of which there would be a presidential election every five years or so at a cost, based on referendum costs, of about £150 million - every five years.
Factor that in and monarchy starts to look like a good deal. There is a case for reform, and a 'slimming down' but this process has already started with the distinction now drawn between working members of the royal family, and those who are not. My view is on balance, taking into account British history and tradition, that at least for the foreseeable future and barring disaster, the British monarchy will be around for a while yet.