I thought I might post this on the D***y M**l thread because after reading some of the comments....... http://www.dailymail.co.uk/sciencetech/article-1330917/Stonehenge-builders-used-ball-bearings-giant-slabs-stone.html and tearing out what little hair I have left I decided to join the comments page (mea culpa) and put the know-nothing numpties right. It wasn't until my green ink had run out that I realised I was limited to 1'000 characters not 1'000 words!
Therefore excuse the hasty precis. The topic is now closed.
Jim.
P.S. I think that the heaviest stone at Avebury is the large Cove Stone at 110 tons+.