Seen a big random rock?

Curious if anyone knows the location of any large-ish, out-of-place rocks in and around London. Trying to map out locations of glacial erratics (rocks that were carried over here by glaciers way back when) and figured some of you have encountered some on hikes, walks, etc.

By big, I just mean you wouldn’t be able to lift it. They can be enormous - they size of houses, but are usually just smaller - like a big ornamental garden rock the size of a large dog, or something.

Thanks so much!