If nothing else it could easily be a passage tomb! It might sound daft, but the one Stukely drawing of the tomb inside Avebury isn't too unlike the passage tomb inside the Giant's Ring just outside Belfast.

The shape's right and the size isn't unrealistic either.

It's certainly a good looking lump.

Tells it all, doesn't it!

There is a map in the Red Lion which has it marked as
"The Great Bank"
How do I go about Proving its anacient?
There is a lots of rubbish at the top, esecially on the left above the spring, but very little on the right leading down to the pond.
The bottom of the mound is Clean IE: good soil with lumps of flint and sarcen in it. There are alot of small sarcens around the bottom and several sizable ones halfway down the mound which could have been knocked down from the top.
PeteG