I certainly agree that Avebury is spectacular and may have been multi-functional. I also agree that people were probably drawn to it from a very wide area and maybe even from Europe. Perhaps the Swiss Amesbury Archer took it in on his wanderings.
The moat idea just doesn't hold water. Think about it - where is the water going to be drawn from? The rivers. Ok, so how do you get it to the Avebury ditch? Buckets or pipes and pumps? The water would drain through chalk as quick as you could fill it unless the ground was already temporarily water logged from heavy rain - so a seasonal moat perhaps? Finally - surely there would have to be traces of waterproofing clay or sediment. I believe that the ditches have been excavated to undisturbed levels and no such evidence has been found. Why would you want to put a moat around a pig pen anyway? Can pigs not swim?.
