Largely thanks to the rich person’s conifer craze in the 1800s- I love that quite often, the actual estate and mansion is completely gone, the family’s died out but the trees remain. Imagine going to Bob the gardener with a sapling or seed and saying, plant it carefully, it could live for centuries and grow to be the biggest tree in the country. Always love finding them
My old work was built on the site of an abandoned stately home, I had one of the oldest giant redwoods in europe right outside my window. Just a tiddler though really! Managed to get some saplings to grow from its cones, but never had any survive past a couple of inches.