I wonder who owns these land.

The government believes 57% of rural land is in private hands, with about 12.5% owned by public bodies, 3% under community ownership and about 2.5% is owned by charities and other third sector organisations. The remainder is thought to be owned by smaller estates and farms which are not recorded in those figures.

That's weird enough, isn't it? In the Czech Republic, such "projects" tend to use so-called white horses, on which the company is written. When it comes to depth, it can be found that this "white horse" has no powers and, conversely, the powers usually have a society that comes, for example, from the Virgin Islands, etc. So it is untraceable. Then it is quite clear to whom it belongs.
I think the lands around the planet that are being built as detention camps belong to the same owner.

The Crown Estate's rural holdings have a more precise measurement, according to its website. They comprise of agriculture, forest and mineral ownership over roughly 116,000 hectares (286,642 acres). The estate also includes some residential properties scattered across its land.

The world's primary feudal landowner is Queen Elizabeth II. She is Queen of 32 countries, head of a Commonwealth of 54 countries in which a quarter of the world's population lives, and legal owner of about 6.6 billion acres of land, one-sixth of the earth's land surface.