The site talk doesn't make sufficiently clear in mentioning both that the feature on the Ness of Brodgar site (HY31SW 112 at HY303128-303129) is not that chambered tomb (HY31SW20 at HY30391280), and I have heard it several times. And it is now apparent from re-reading the 1849 survey that the latter is the Kokna-cumming "burnt mound" (RCAMS 1946 Inventory 899).
Something is not right. This message is just to keep things from messing up down the road