The 'black spider' letters: Dear Prince Charles, opinions are for abdicators

The heir to the throne likes to make his views known – but not to us. He should learn from his mother, and keep his letters polite and bland

I do rather feel ... The Prince of Wales is an inveterate letter-writer, but expects secrecy

The Queen knows how to handle her correspondence. Write a letter to the monarch and you will be rewarded in kind: not with a message in her own hand, it's true, but a charming substitute from a lady-in-waiting, who will tell you how very pleased the boss was to hear from you, and what an excellent idea it is to have a baking competition in honour of her birthday, but no she sadly won't be available to come along and try one of the cakes and please find the recipe you enclosed returned for safekeeping.

There are, presumably, more revealing letters that remain unseen. But to judge by Elizabeth's generally scrupulous sense of decorum, it is hard to imagine they are ever anything but proper. The Queen seems to understand that the sort of leadership that we want from her is best expressed through the blandest sort of courtesy. She is a slate so blank that when she made some entirely uncontroversial remarks about poverty last week, suggesting that poor people should be helped, they were read like entrails for a hint of her politics. Even this, frankly, seems a bit too much. A twinkle in her eye as she waves is all I want to know about her hinterland. Opinions are for abdicators.

It is certainly hard to imagine her taking on a minister. Not so, you feel, the Prince of Wales, he of the famous "black spiders" – an epithet intended to describe his handwriting in epistles to decision-makers that, instead, conjures up images of the heir to the throne as leader of the Windsor branch of the Hell's Angels. Prince Charles is well known for his determination to let anyone in power know exactly what he thinks they should do, mostly by post.

He makes for a peculiar sort of professional lobbyist. As such, you might hope that he would go out of his way to advocate the sort of causes that would appeal to the widest range of his 60 million or so employers. To judge by the available evidence, though, that's not the case. The few letters of his that we do have access to suggest that he views himself exclusively as the divinely appointed representative of people who wear red trousers. "Our lives are becoming ruled by a truly absurd degree of politically correct interference," he told the Lord Chancellor in 2001; the farmer had been right, he grumbled to Tony Blair in 2002, who told him that "if we, as a group, were black or gay, we would not be victimised or picked upon".

If those are the ones we're allowed to see, what about the rest? In the main, we're in the dark. But last week, the Court of Appeal dared to affront the monarchists with a decision of refreshing common sense that brings us a step closer to knowing what at least some of those letters say. The Guardian's Rob Evans has been trying to get access to the letters for years, not unreasonably arguing that if Charles is exerting an influence on policy then in a democratic country we ought to know about it. So far he has been thwarted; in October 2012, the attorney-general Dominic Grieve overruled a court's decision to allow access. But last week, Grieve lost an important battle. Now, barring a successful appeal to the Supreme Court, Charles's correspondence will be revealed at last.

About bloody time. Grieve himself called the letters "particularly frank", but should you have had any doubts about their controversial nature, you would have had them dispelled last week: when the arguments are sofeeble, you wonder how embarrassing the material they are trying to hide must be. Grieve himself has been keeping a low profile, but Michael Ellis, a Tory backbencher, made the case against access on Radio 4's PM, and the holes in his case were so enormous that you could park the gold state coach in them.

To begin with, he claimed, Charles was being denied the same right to privacy that any constituent could expect – as if he were writing to his local MP about a leak in the Clarence House roof. He echoed Grieve's ludicrous suggestion that the sacred principle of royal neutrality would be compromised by publishing the "particularly frank" letters, whereas anyone reasonable can see that the thing compromising the sacred principle was writing them. And he trotted out the bizarre argument that this 65-year-old man needed to be able to write private letters to ministers as part of a kind of on-the-job training scheme: "We simply can't have a system," he harrumphed, "where on day one of the new reign we expect the Prince of Wales to function as if he were monarch."

This is a fair argument, of course, if the new king in question is in Game of Thrones, taking charge of the fictional kingdom of Westeros, and charged with momentous decisions about who to execute and how to defend the empire against the Dothraki invasion from across the sea. But with a bit of luck, and barring something really weird happening in France, this won't be part of Charles's duties. Mainly, he will have to smile, and wave, and say something nice to help your Christmas pudding go down. I think he can handle it.

This legal battle has already cost the taxpayer hundreds of thousands; if Grieve has any guts or shame, he will now give it up. But I wouldn't hold your breath. Since the original request to see the letters went in, things have actually got worse: in 2010, parliament reverted to its medieval model and waved through a royal exemption for the Freedom of Information Act. And so, from here on in, an unelected and very rich man with insidious authority will be able to write secret letters urging policy changes without fearing any sort of oversight. Meanwhile, another legal anachronism has allowed the royals to veto laws that affect their interests – a power that the current generation of Windsors have been offered 39 times. We would be furious if it was Murdoch.

If Charles and the rest of his family consider this a positive development, they should tread carefully. We are mostly monarchists in this country, but only in the sense that we enjoy them as part of the furniture: harmless posh mascots who go to terrible clubs and play polo and in general add to the gaiety of the nation.

The republican movement has no momentum whatsoever, but we are a resolutely undeferential bunch these days, and I have a hunch that it wouldn't take much to get the revolutionary ball rolling. If he has any sense, Charles will learn to keep the poison out of his black spiders. And if the ministers he is writing to have spines, I hope they will learn something from his mother when she gets unsolicited mail from eccentrics, and write back with the utmost politeness – and very short shrift.