The difference between the first diagram, produced in 1930 and the last in the set, produced in 1948 can be seen here. It is a really clear illustration of how much the electricity industry advanced in those years and where the developments in the infrastructure occurred. The plans clearly show the gradual build-up of an electricity network in an area that was initially not attractive to local authorities, and demonstrate the rural electrification of remote areas, linking farms, collieries and other businesses to the system.