Google Earth, presumably a recent image, seems to show that there had been a recent slip just there before the vegetation clearance had taken place. That looks more like a slip than clearance.
https://www.google.co.uk/maps/@51.6882017,-0.426319,109m/data=!3m1!1e3
Also there appears to be major construction work immediately at the top of the bank, which may have affected the ground water table.
https://www.google.co.uk/maps/@51.6882017,-0.426319,109m/data=!3m1!1e3
Also there appears to be major construction work immediately at the top of the bank, which may have affected the ground water table.
