Bookworm,
Can you think of any example of normal operation where you would need to land before the threshold?
If you were an aerodrome owner who designated a threshold for safety reasons would you then ever permit any flight to land before it?
What would your legal position be if an aircraft can't land at your aerodrome because the declared runway is not long enough so you give permission for them to land before the threshold and they clip the hedge on the way in or have any other form of accident in the undershoot (area before the threshold) followed by them passing on a copy of your "permission" to their legal team / your insurance company?
Purchase a big field in the middle of nowhere, plough it up and then land your piston hotship on it. Noting illegal there.............other than the reckless way in which the operation was conducted. Of course if you don't care about breaking your aircraft, you don't claim any insurance and you don't injure yourself then you can do it again and again until you grow tired of breaking aeroplanes!!
Regards,
DFC