A nice little earner.

As a royal author, I have come across plentiful examples of royal greed. It is standard practice for the royals to seek to minimise their personal expenditure while maximising their income from other sources, normally the public purse.

I think by “minimise their personal expenditure” he means not “spend less” but “spend other people’s money.”

But the revelation that King Charles III’s personal slush fund, the Duchy of Lancaster, is having its already bulging coffers augmented by the estates of people who die in parts of England with historical links to the royal estate plumbs new depths of disgusting avarice.

Like many so-called traditions, the feudal hangover that is bona vacantia should have been consigned to the dustbin of history centuries ago, but it has been all too tempting for successive royals to preserve this royal fruit machine that pays out again and again. Over the past 10 years, it has collected more than £60m.

Well if we went around consigning feudal hangovers to the dustbin of history where would that leave Choss Windsor?

Under this system, the Duchy of Cornwall, owned by Prince William, can claim the assets of people who die in Cornwall intestate – without a will – if no relatives can be found. Charles’s Duchy of Lancaster does the same when their last known residence is within what was historically known as Lancashire county palatine.

“Cornwall for me, Dad, and Lancs for you.”

George VI did very well out of the loyal servicemen who died serving their country in the second world war, who originated from within the confines of the duchy and had no will. “For king and country” took on a whole new meaning.

As disquiet about the practice of bona vacantia grew after the war, the royals announced that moneys collected would henceforth be given to charity – after processing costs had been deducted, of course.

But only then, eh? “All right all right if you’re going to make such a big fuss about all this free money we get for existing.”

Yet a Guardian investigation now reveals that matters are even worse than we have been led to believe. Put bluntly, we have been lied to. Moneys we all thought were going to charity have instead been used to improve properties owned by the duchy, increasing the income stream that flows from them into Charles’s pockets.

We have the most expensive monarchy in Europe by far in terms of state support, and one that benefits from unique tax treatment available to nobody else. No inheritance tax is paid. The so-called private estates of the duchies of Cornwall and Lancaster are not private enough to pay corporation tax or capital gains tax. Even income tax is only paid voluntarily – if it all – no receipts have ever been made public.

The civil list, which in 2011 gave the royals £7.9m a year, was replaced, after palace lobbying, with the sovereign grant, which 12 years later is up to £86m a year.

Over the centuries, the royals have continually bleated poverty and demanded more money from the taxpayer, while at the same time refusing point blank to reveal the extent of their accumulated wealth.

And they’re still doing their best to hide the extent of their wealth. Choss didn’t tell us about this bona vacantia wheeze himself, you’ll notice.

It’s not as if he invented the internet.