Passed this low-lying fort after a trip to Windmill Tump today. Approached from the west along the disused Thames and Severn Canal. The west side of the fort (which is all I saw as the rest is on private land) appears to be a steep bank, but as the canal ran alongside it’s difficult to know what was fort and what was canal engineering.
Of interest is the fact that the spring source of the River Thames is at the southern tip of the fort. As the Thames was venerated by the Iron Age people (witness the number of swords and other offerings thrown in further downstream), it may be that this had some significance in the siting of the fort.