I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
Castle is at the end of a private road. Park in Garstang (Sainsburys) - the ruin is a 10 min (easy) walk from there. Cars not permitted on the private road. Alternatively, the ruin is easily reached from the canal towpath nearby.
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 13/09/2020. It remains the responsibility of any pilot to check for any changes before flying at the same location.