INFORMATION:

The Antitank ditch using concrete and local Flint Stone.

I think this was a converted HA HA. A wall with a ditch in front, used in large country houses. When looking from the house you cannot see the wall and the eye is deceived into thinking the garden and field are one and the animals cannot get to the garden because of the wall & ditch.

The HA HA was strengthened with concrete and incorporated into the defense.