As a common feature of wall gardens over a period of the time, the soil soaks up the rainwater which penetrates the brick and a freeze/thaw situation occurs.
This systematically blows the face of the brick until eventually the whole brick disintegrates causing the wall to collapse.
Early repairs will prevent the latter from happening and bring the wall back to its former glory
Hence the old bricks were removed and the damamged wall was rebuilt as can be seen in the photos (the new bricks will obviously stand out for some time until they weather and blend in the existing bricks)
