NSW Neighbour removed retaining wall and my land is collapsing

Hi everybody,

My neighbour recently built an extension and it appears that in order to do this, they removed the retaining wall from the boundary. The fence has started to tip over and chunks of my land has started to fall into their garden. The neighbour came over with a dodgy looking quote and demanded WE pay almost 2K to put the retaining wall back in and fix the fence. We took photos which clearly show that the wall has been excavated and took it to council. After making us wait for months, the council have told us they sent us a letter over a month ago to say it was a civil matter. Any advice? Thanks.

Thanks Rod & Clancy, and apologies for the delay in responding to you both. I'm going to try neighbourhood dispute resolution with the option of a civil suit if I get no joy. I have photographs from their side which clearly shows the exposed footings (chunks of concrete) of the fence posts. They recently built an extension to the rear of the house and it looks like the retaining wall was removed to allow greater access to this and also the concrete slab appears to stretch as far as the boundary. The neighbour has not spoken to us since we confronted him with that information.