Couldn't find anything under "Circles under churches" - an interesting thread, but the posting where it says "that brings us back to the question of a roof" is under the thread "Stonehenge lintel holes".

To extend on my previous point about over-engineering, this is a quote from A. Gibson “Stonehenge and Timber Circles”, Tempus Publishing Ltd (2005).

"Why was it necessary to continuously pound, day after wearing day, at the top of a sarsen to crush away the majority of the stone while leaving one (or maybe two) large tenon standing proud at the top of the stone? Why was it necessary to exercise much effort and spend considerable time hollowing out two mortice holes on the underside of each lintel? Why was it necessary to ensure that each lintel could be fixed to its neighbour by laboriously fashioning a tongue at one end and a groove at the other? The fact is that the prehistoric builders of Stonehenge were completely wasting their collective time! Weighing in at 7 tons, each lintel needed no fixing, their sheer weight would have ensured that they stayed in place. It is much more likely that these architectural devices were used because that was the tradition within which Stonehenge’s builders were working. The Stonehenge lintels were fixed to their uprights in a manner usual for such monuments. This was how it was done, not how it needed to be done. There is another explanation. The mortice and tenon joints, unlike the norm in joinery do not completely pierce the stone. They are not mortice and tenon in the strict sense but rather they are ball and socket joints which allow the stones to swivel to a certain degree. Thus when the lintels were being lowered into their final positions on top of the sarsen uprights, the ball and sockets would have engaged and acted as a self righting mechanism, guiding the lintels into their precise position with far less effort than would have been necessary were they to have been levered to and fro in an attempt to exact their positioning."

The first point suggests that the Stonehenge builders did not know what they were doing which is pretty contentious.

As for the second point, surely the stones could have been guided to their final resting position using a simple wooden frame.

Chris W