Ah, right, nowt right there though? That weakens my attempt at comparison a bit, but I'm still thinking of a couple of places I've been, where there are weird shaped natural rocks surrounded by seemingly purposeless ramparts.

In particular, I'm struck by the fact that the other, un-ramparted Tor is higher, and it seems plain daft to build a fort/defensive thing in a position where adversaries could get above you and lob missiles. That and the basin adorned chair stone remind me lots of The Piper's Chair. One of those defensive sites that just doesn't easily fit into a category, but is spatially focused on some odd rock formations with natural basins.