Legal boundary vs physical fence
The fence you can see on the ground and the legal boundary are not necessarily the same thing.
Why this matters
A replacement fence can end up slightly inside or outside the old line, and the old fence itself may never have sat exactly on the legal boundary. That means “the old fence was here” is useful evidence, but not always the final answer.
Start with documents, then inspect the site
Check the title register, title plan and any filed conveyance or transfer. Then compare those documents with physical features such as old posts, walls, hedges, ditches, building corners and long-standing markers.
Do not measure the red line with a ruler
The red edging on a standard title plan is not a survey-quality line showing the exact boundary to centimetre accuracy. If the exact position is disputed, a suitably experienced boundary surveyor may be needed.
Related tool
Use the Fence Dispute Helper if the physical fence position itself is being challenged.