"So the Barnhouse Stone is perhaps only 'the tip of an iceberg'."

Aye, I couldn't help but wonder how far it goes down. 3.5m above ground, and still pretty much totally vertical, pretty impressive engineering, there must be some whopping packing stones at it's base.
I was surprised at the thickness of these slabs, they are thicker than I thought they would be, as they are taller than I imagined. The stresses on them whilst they were being shifted must have been substantial though. I would have been a bit worried if I was the dude who had to drive the posts for the sheep fence. Worried that the movement could have dislodged a packing stone or something, leading to lethal stone toppling.

For my money, Barnhouse has more 'oompf' than any of the single stones at Stenness and Brogar, mostly because the vegetation on it seemed to hammer home the fact that it hasn't moved in a long long time. It's almost Tolkeinesque.

Kammer's fieldnotes make a good point, it's sadly neglected cos of the others nearby, especially as from the road it looks small, but maybe that's why it's kept it's integrity, 'cos it's been largely overlooked.

We managed to catch a couple of tombs too, courtesy of M&J, I think I'm a convert. They're ace. Only 2 days on the island, and it's given me so much to think about.