Ask an Property Solicitor. Get an Answer ASAP.
Hello Brian my name is ***** ***** I will help you with this.
What is it you want to achieve please?
Ok - you should report it to the Police. They can consider this for criminal damage if things are being attached, screwed or affixed to your fence. The Police may try and say it is a civil matter, but it is not, it is criminal damage.
If that does not work then get a local Solicitor to write and ask him to stop and re-instate the old fence. Unless your deeds stated otherwise then it is a joint fence and needs to be reinstated.
If that does not work you could get a Court order making him reinstate the fence.
Can I clarify anything for you about this today please?