Trethevy Quoit 11
Image by heptangle

That's very true, none supporting stones could have fell over time and being moved about, one big job would like you said have probably been known about, I didn't think Roy was saying one big change, just that things fell when the capstone slipped, was that reported - when it slipped?

Doesn't seem to have been, but by 1850 the capstone was no longer supported by 5 uprights, so it seems likely to have been some time between 1824 and 1850.

But. I've no idea what angle the capstone was at in 1824.