Very strange. So farmers can neglect their property (fence) as long it borders the railway line.
As mentioned by others, railway boundary fencing is normally the responsibility of the railway. NR have a duty to maintain that fence to a reasonable standard but that does not include keeping every animal or person out under any circumstances.
As a junior draughtsman, one of my first duties was investigating "sheep claims", which included other animals. Farmers can claim for loss of livestock under certain circumstances. Part of my job was to try and trace the route the animals took to enter railway property. If I could demonstrate that the animals had left the farmer's land and entered other land BEFORE getting on the railway, the claim was rejected. It was also not unknown for an unscrupulous farmer to cut the fence and drive inferior animals onto the line to make an inflated claim.
A well maintained 5 strand post and wire fence was the required standard. Again, my memory may fail me, but I seem to recall that a farmer wanting to keep young lambs in an adjacent field had to inform the railway so the additional 2 lower wires could be fitted to the 5 strand fence.
Perhaps that has changed but I believe the modern high steel fencing is railway inspired to cut down trespass to suit the railway's own requirements.
