I’m not a “royalist”. Nobody in Britain is now in the old civil war sense of course, and I’m not one in the newer sense of loving the pageantry and froth that goes with royal occasions. In fact I used to be a republican, when I was sixteen and put pure abstract perfection above sense in matters constitutional.

But I don’t think like that now. In my view constitutional monarchy, along the sort of lines we have in Britain, is an excellent constitutional model, fully the equal of any alternative – and in some respects arguably better. We should stay with it. It’s time for the country to grow up, and turn decisively away from the case for change put forward by campaigners like Republic.

It’s true that we could move to having an elected President with largely ceremonial duties and some reserve constitutional powers – the sort of President they have in good democracies like Germany and Ireland. But why should we? In effect we already have this sort of head of state – we just call her our Queen. She’s unelected, of course. But if the President would have little or no political power (as the Queen does now), what, in a sense, is the point of electing him or her? Of course what the President does could matter a great deal in a moment of constitutional crisis – but those events are unpredictable, so it’s impossible to vote for someone today having any real idea of what the person could do in an unforeseeable moment of crisis.

The problem about electing a president is that the head of state would be yet another politician, probably supported by one of the parties. We’d be faced with serious questions about what electoral system to use, we’d worry about what would almost certainly be a very low turnout, and the candidates could well be either very bland ex-ministers or else semi-celebrity politicians of the Ken and Boris type. What would the term of office be, and when would elections be held? Would the President be chosen at general election time, and so probably be of the governing party? Would it be a mid-term choice, probably of an old opposition figure? The more you think about these issues, the more you realise that we’d be replacing a system that works well and is popular with one that would be risky and might quickly become discredited.

The very strength of the monarchy is that the Queen is not a politician identified with any political past or party. If a constitutional crisis occurs, whatever biases people might feel our current or future monarchs suffer from they have no ideological or tribal loyalty to any of our parties.

If we did elect a President, we’d probably decide we needed to specify more precisely the extent of his or her reserve powers – and indeed, Republic does want a written constitution. But that’d be a mistake for Britain, our unwritten constitution being one of our greatest strengths. In a constitutional crisis, the very uncertainty created by unwritten conventions and precedents means that politicians are forced to act cautiously and behave in ways they claim represent propriety – they cannot instead claim written rights or dispute them. Nor can they turn to the courts to ask judges to give them victory. The useful uncertainty built in to our system is too often unnoticed. It’s built in, for instance, to the convention – only a convention, you’ll note – that the Queen gives Royal assent to Parliamentary bills. It used to be built in to the arrangement surrounding the Queen’s power to grant or refuse a dissolution of Parliament and a general election – until this government got through its awful, unwise Fixed-term Parliaments Act. That’s an unhelpful piece of ad-hoc written constitutionalising that I hope’s repealed in the next Parliament.

Other countries, forced to create their own constitutional arrangements from scratch, have come up with very good designs: the United States and Germany are two excellent examples. I think those constitutions are outstanding achievements that have worked well. They have strengths and flaws, just as our constitution does, but they show us that, when it comes to constitutions, intelligent design can work. We here are lucky, in that we’ve never been forced to rely on intelligent design. Evolution has done its work for us. Over the last two hundred years, for instance, it’s gone further in reducing the power of the monarch than America’s founding fathers did when they reduced the King’s powers and subjected him to election as President. Evolution does well, too, as a method of making constitutions fit for the social environment.

Nor is Britain alone. We like to flatter ourselves that archaism and quirkiness are unique to Britain, and in our most hair-shirted moments feel the urge to sweep them all away so we can be shiny and modern like “everyone else”. But in fact many countries have similar constitutional arrangements to ours – in particular, quite a few of them are constitutional monarchies. Constitutional monarchy is in no sense an unusual, isolated or outmoded choice.

If you list the world’s major constitutional monarchies – the Netherlands, Denmark, Sweden, Norway, Belgium and Spain; Canada, Australia and New Zealand, all of which share our monarch; and Japan – you realise that these are some of the best, most egalitarian and socially progressive societies in which anyone lives. This should make those on the left of politics especially think twice about change.

Republicanism is for puritans, purists and those who love to daydream about fixing what ain’t broke. Let’s keep our perfectly sound constitutional monarchy.