However, on looking closer, I could see daylight through the crack, almost from top to bottom...panic!
So out came the grinder and I cut the crack wide open, in order that I could fill the space with cement, not just cosmetically cover the crack.
It could have been a lot easier, but for some reason that we yet have to fathom, our neighbour has had a funny turn, and again is being awkward, she will not give me access to do any work to our walls. This is strange because some time ago, she was having some fencing problems, and I offered to go and fix them for her, but when I went round, her son (Druggie) said they didn't need help, his Brother would come and do the work (he still hasn't done any of it!!), any way I only offer twice, she can get on with it.
I went up the ladder and had a peek over the wall, I wanted to find out what the problem was, as I had done a repair on the same place, soon after we moved in, and the answer was there staring me in the face, it is not one wall, but two, and they are not tied into each other! The join is the crack, I think an earthquake we had a couple of months ago, that gave me cause for concern, was probably the culprit in this case.
There is a secondary problem, that I can not do anything about, unless our neighbour has a change of heart, and that is that their land is on a higher level than ours, and the wall was constructed without any protection, so the water is seeping through from her side, causing problems on mine, I guess that in years to come the brickwork will disintegrate and collapse, but for now, I have to keep patching the render and repainting.