"Cropmark noted from an aerial photograph (Fraser, R, NAA 94/1/0. SMR F.I. Files, 1994, Filed under AP collection NZ21SE). At least three circular marks are visible. The 2 smaller circles are approximately 20 metres in diameter, suggesting an iron-age or Romano-British date. The largest of the circular features is approximately 50 metres in diameter and may therefore be an earlier prehistoric feature." (County Durham Sites & Monuments Register)
The map reference given here is accurate to within 1km.