I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
The castle itself is closed to visitors on Saturdays, but the rest of the week is open as it houses a collection of classic cars.
There are plenty of quiet roads around with areas you can pull into to safely take off and land.
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 28/08/2021. It remains the responsibility of any pilot to check for any changes before flying at the same location.