It is at the front of the house, and both of our gutters go into the same down pipe which goes into this drain and consequently into our main one instead of theirs. We each have our own manhole access.Is it a storm drain? Does your and your neigbours guttering drain into it?
Post a pciture from the rear of the garden looking back at the house.
Andy
Middle pipe in picture is from the gutters. Other two are soil pipes.