Neighbour disputes the boundary line after twenty years

What we told them

Find out which document governs before you argue about the survey. Registered title plans are indicative, not definitive, and a twenty-year-old fence may have established a boundary regardless of what the paper says. Get your own copy of the title register and any historic conveyance, then take both to a surveyor who does boundary work specifically. Do not move the fence and do not agree to anything in writing until you know which record wins.