Neighbour erected fence in my garden

Old_Git

My neighbour has erected a fence which I think may be in my garden .
How do I check the measurements before I speak to the neighbour .
I dont have the deeds but I gather I can get them online .

I am in Northern Ireland .https://www.nidirect.gov.uk/articles/searching-the-land-registryFees to search and copy Land Registry documents
There are fees to search and copy documents:

£5.00 for inspection of each folio, map or instrument
£5.00 for inspection of the Index of Names for one name
£7.00 for an uncertified copy folio/instrument
£17.00 for a certified copy folio / instrument
£7.00 for an uncertified copy of the Registry Map
£17.00 for a certified copy of the Registry Map, not showing appurtenant rights
£51.00 for a certified copy of the Registry Map, showing appurtenant rights

Appurtenant rights
An appurtenant right is attached to land and gives the landowner a benefit, for example a right of way over neighbouring land.

There is no right of way

What part do I need to purchase .

Davesnave

I'm not familiar with NI law and documentation, but the same practical constraints apply to the use of maps and plans in determining boundaries, wherever one lives.

A line on an OS map or plan is usually taken to show within about 0.4m accuracy where a boundary is in the real world, thus giving scope for disagreements over small slivers of land.

However, if a boundary on a plan is straight and the fence marking it is crooked, or there's some permanent reference point, like the corner of a building, then it may be possible to use the plan as hard evidence of something awry in the real world.

Pertinent questions here seem to be, how long ago was the fence erected and what's changed? For example, there's another thread in 'In My Home' running currently where the OP says a fence was erected wrongly in the 1950s. To most of us, that would not be a situation one could challenge successfully now, since adverse possession would apply.