I'm a bit unclear as to the workings of henge corrals. How deep, how high and how vertical would the walls need to be. How soon would they erode, is there evidence they were re-cut, would they be used in conjunction with a fence (in which case, why not just use a fence?)
Would the animals be allowed into the ditch? Presumably, else if there was a fence to keep them out of it, what's the point of the ditch or the bank?