I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
There is a car park at the site and a lay-by on the road. It's a 5 minute walk to the hill.
Silbury Hill is the largest human-built mound in Europe, begun sometime between 2500 and 2900 BC. In sheer volume of material, it rivals the Great Pyramids of Egypt. It has been estimated that it would have taken a team of 500 men about 15 years to complete Silbury Hill, and then only if they were working continuously.
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 09/10/2021. It remains the responsibility of any pilot to check for any changes before flying at the same location.