Historic England's record says that the round barrow here is a respectable 3m high. It's on a prominent hill and there's a photo on the 'Earthworks' blog that makes it look mysterious with its cap of trees. The area sounds like it's full of weirdness (as you can read). But regarding the barrow itself, to quote the blog...
Local children often call this 'the witches hill'.
Various signs of veneration can often still be found on Hagworm hill. A clay figure of a Mother Goddess, obviously made fairly recently, and coloured rags tied in the thorn tree on the summit of the hill. Painted egg shells, and a small stick carved with runes. All these and others have been noticed left on the hill by people who still regard this as a sacred place.
I was also told by a local man that as a child he and his friends believed it was a flying saucer that had crashed many years before and become grown over with trees, and that the aliens still lived inside, though his parents told him this was not true, as it was fairies that lived inside the hill. Each generation has its own little green men.
The Earthworks blog is full of interesting landscapey fortean things.
The OED says a hagworm is "A northern name for the adder or viper; but in some districts applied to the common snake, and in others to the blindworm" (the latter being the slowworm).