I can't take the credit for the full operation. Half an hour moving stones away from the collapsed wall, three hours to build the wall up to the level of the ground beyond the wall and half an hour spent lobbing the remaining stones over the wall for the build to be completed from the other side.
One of my woodland neighbours kindly spent a further three hours completing the build, taking the total man-hours to seven.
It is a tricky location since, as well as being on a considerable slope, the location suffers from a wind-funnel effect due to the rock outcrop beyond the wall.
Here is the starting point.
NY1404 : Collapsed Wall