Trouble is that there are more than 3 henges on the Ure Swale plateau
So where do Cana, Hutton Moor and Nunwick fit into the stella picture?

Personnally, I'm pushing my own theory, which is of course based on nothing more than this week's whim, the large henges at Thornborough represent the Temple of the Triple Goddess and her three northern tribes
or possibly a bunch of late Neolithic Tykes showing the Cumbrians and the Wessex Folk that we can build bigger and better.