The same families that were wealthy three hundred years ago are still wealthy in the UK, roughly speaking.

That makes the UK seem pretty corrupt. Do you have any sources for this?

You would need to get a record of who was wealthy 300 years ago, track down their descendents, and see who among those descendants is "wealthy" by some measure today.

You might also need to take into account things like inheritance and birthrights. I imagine first born sons of first born sons might preserve more of the wealth.

Also, what proportion of the rich today are "new rich", and how newly rich are they?

Define it however you like but a lot of UK land has stayed within the same families for generations.

It's not unusual by any means. There was a study on, I think, Genoese families that showed that wealth had more or less stayed within the same families for 300 years.

Inheritance isn't normally a corrupt practice, and the best way to get lots of money is to start with lots of money and accrue it.

So the Industrial Revolution didn't shake up the structure of the elite?

In Europe some families are still insanely rich from being rich 500 years ago. There's not much being written about them today as many do not seek publicity.

Thomas Picketty's "Capital in the Twenty-First Century" is best known for central its argument that wealth will concentrate in the long term, but it also extensively documents the European generational wealth that was destroyed in the first half of the 20th century. Two wars, a great depression, inflation, and high taxes were enough to permanently ruin the accumulated capital of many families.

So it's true that some families that were wealthy 500 years ago are still wealthy today, but this was not the norm.

I'm not convinced the ultra-wealthy of the 19th century are not, largely, very wealthy today.