Assuming triangular sections, my calculations show a maximum height of 12m if the hill was created solely from ditch material, a significant difference from the EH figure. It’s probably a coincidence, but the angle of slope created by a height of 12m gives 31 degrees, almost exactly the angle of slope of Silbury Hill. Given the nature of the greensand, I’d be surprised if the mound could have been any higher, as the angle of repose (maximum “steepness”) of dry sand is 32 degrees, 35 for wet sand. A height of 15m would have required an angle of 38 degrees.

Second, the chalk floor is obviously of interest, as it seems to have been specially imported. And that raises the question of whether the chalk itself is sacred. My feeling is that the chalk landscapes of Avebury and Stonehenge are in some way sacred through the medium of the brilliant white chalk, and that special quality was imported into Marden.

Alex Down