I remember a case in the PFA Magazine about 12 years ago. Established private strip bordered a neighbouring property so takeoffs or landings had to pass over this property.
Property changed ownership and new owner immediately erected poles on his property about 30 ft high just off the end of the runway. The article included a photo of the end of the runway showing the poles which were clearly a 'hazardous' obstruction.
Strip owner objected on the grounds of Art 73 (Art 65 in those days if I remember), but in court I think it his plea failed as although it was an 'established use', it was an unlicensed airfield.