In the fields at the foot of Oliver's Castle, there is a small wild wood, with tangled undergrowth from which emerges a lively stream (carrying a surprising amount of water) at its western edge. This wood is marked on the OS map as Mother Anthony's Well. Access to the interior was difficult, but once inside the wood,there are springs in abundance.
We had given up on finding the well in the wood and were walking around its perimeter to retrace our steps back up to Oliver's Castle when we heard the clear sound of running water - and there it was, forming a small pool before falling into a fast flowing stream.
It is reputed to be the site of a Romano-British shrine, but archaeological finds there put its use back well into prehistoric times: flint tools from the Mesolithic and Neolithic; a Neolithic axehead and pottery fragments; Bronze age pottery and flint tools; and various objects from the Iron age, including a brooch, a ring and a whetstone.
ref: (Wiltshire and Swindon History Centre Sites and Monuments Record).
The hummocky hillock landscape on the 'other side' of Roundway Down has an ancient, odd feel to it - hard to describe, walking through it is recommended.