When visiting Knowlton Henge the barrow is unmissable.
It is in a private field next to the henge (full of sheep at the time) and does not have a public right of way to it. The field is overlooked by a farm house who I assume own the field?
If you want to access the field for a closer look it is easy over a low metal fence.
I chose to view from the henge as there didn’t seem much to gain from getting closer – other than perhaps an upset farmer?
The barrow is large but totally overgrown with several large trees and many bushes.
I would imagine climbing to the top of it would be tricky.