Electrification for the passenger meant a more reliable service and faster journeys. For the railway electrical engineer, however, there were some significant hurdles to think about, such as substations, feeder stations and strategic neutral sections to prevent overload on the National Grid. The civil engineers had their hands full too, with considerable bridge and lineside structure rebuilding to be carried out - all while keeping the lines open to everyday traffic. This film examines the trials, tribulations and learning curves that British Railways underwent as it proceeded to install a modern overhead electrified railway. It presents us a technical explanation of just some of the apparatus involved, and difficulties overcome, in a new field of railway engineering at the industrial frequency of 25kv AC.