Colin Brazier: The Royal Family isn’t finished, but it’s in more trouble than many of its supporters have noticed

It’s time to make-up your mind about Prince Charles - why? Because the anti-monarchists are on the march. They can hardly contain themselves.

The Queen may be in good health, but today billboards have sprung up in Cardiff, paid for by a Republican group, with a picture of the Prince of Wales and the words “Wales doesn’t need a Prince”.

Abolitionists smell blue-blood in the water. Two thirds of Britons still support the monarchy, but among the young, fewer than half do. And when the Queen leaves the stage, republicans are poised to pounce. They have a war-chest ready. They will spend it on billboards and newspaper adverts and polling and lobbying and not a few stunts.

Their friends in the media, who hate the idea of deferring to anyone or anything other than their own, will give them plenty of air-time.There will be internet petitions, attracting more than a million e-signatures, paying tribute to the late lamented Queen, but demanding that the show stops with her; that there will never be a King Charles the Third.

The Republicans will turn the monarchy’s greatest asset into its greatest vulnerability. By which I mean they will target the royal walkabout. The Queen is reported to have once said that she has to be seen to be believed. And she has been seen – physically seen – by more than 20 million people during her long reign.

These royal public engagements, the ribbon cutting, the tree planting, the plaque unveiling, are the monarchy’s bread and butter. Charles does hundreds of them every year. They are a chance for him to connect with his future subjects directly. What would it take for a few hecklers or egg-throwers to make these appearances untenable?

If 30 eco-activists can close the M25, you can imagine it wouldn’t take more than a handful of Republican protesters to break the spell of the royal walkabout, to stop them being an occasion where the Crown is the object of universal acclaim, to something more like the reality. An institution which most people like, but a small minority loathe.So what to do?

If you’re a monarchist like me, who believes that an unelected sovereign gives our country something an elected president never can, what hope do you have? How can the Palace head-off the coming Republican onslaught?

Well, it has a Three Prince Problem.

Andrew is the biggest liability and must go to ground, for good. I know he’s broken no laws, but the monarchy is an institution founded on public feeling and the public feel nothing but contempt for the Queen’s least likeable son.

Charles, as anyone who’s met him, is a massive improvement on Andrew. A deeply kind and thoughtful man who, as recent embarrassing stories in the Sunday Times have shown, is apt to get involved in controversies he should avoid. He needs to make a public statement that, from now on, he intends to get ready to replace the Queen, by acting more like her – and saying nothing tendentious, ever.

And then there’s William. He’s a star, and his star rises further with every photo and fatuous interview given by his feckless brother Harry. But William’s popularity is actually a problem for the monarchy. Some people want the Crown to skip Charles and pass straight to the Duke of Cambridge. Like many simple and attractive solutions, it does not survive close inspection. The defining characteristic of monarchy is that it's hereditary. There will be good heirs to the throne and bad ones, good kings and bad; there have been for centuries.

But if you drop that hereditary principle the whole edifice collapses. William will get his turn, but when his father dies, not before.

The Crown isn’t finished, but it’s in more trouble than many of its supporters have noticed. It’s time for monarchists to understand what Republicans are planning, and prepare the case for the defence.

That's tonight's Brazier Angle.