...behind the house on a small edge set back just left from the old aqueduct.
As I said really boss ...
Its Chatsworth Estate Ru, no Access issues I would have thought as there are many tracks in the woods behind the house that are open to walkers & people mooch about there all the time seeking the Hunting Tower & Aqueduct etc.
The Grounds staff that I talked to seemed very laid back about my mooching.