Complex sentence: The Longside had replaced the Star Stand in the years between the World Wars, but only the lower areas of the stand were concreted, this had changed by 1954, when the remainder of the stand was concreted over and the roof fitted.
Split into simpler sentences: The Longside had replaced the Star Stand in the years between the World Wars, but only the lower areas of the stand were concreted. This had changed by 1954, when the remainder of the stand was concreted over and the roof fitted.