Complex sentence: It recommended increases in pay and improvements in conditions, which the mine-owners agreed, and also that African miners should be eligible for jobs previously reserved for European miners, which was not implemented then, but was gradually introduced after 1943.
Split into simpler sentences: It recommended increases in pay and improvements in conditions, which the mine-owners agreed, and also that African miners should be eligible for jobs previously reserved for European miners. This last recommendation was not implemented then, but was gradually introduced after 1943.