Hi tjj
As I recall (albeit back in 2006) I just walked up to the dolmen and had an (extended) look. The Bryn-yr-hen-Bobl, a short distance away, was more problematic due to 'insurance'. I therefore wrote to the Marquess and received permission. I understand that gentleman has now passed on, but presumably his descendant has the same appreciation. Drop a note to:
The Marquess of Anglesey,
Plas Newydd,
Llanfair P.G.
Anglesey,
North Wales LL61 6DZ