The paper deals with the electrical installation of the Shell Centre, the central office of the Royal Dutch/Shell group of companies in London and the largest fully air-conditioned building in Europe. A brief description of the buildings is given, followed by an account of the progress of the design from the provision of electrical supplies and a description of the high-voltage and low-voltage distribution.Electrical supplies from two separate sources enable half the lighting to be connected to each supply and all power plants to be switched to either supply. Most floors above ground level are laid out on the same general lines as standard office floors and divided into offices by demountable partitions. Switching of the lights can be adjusted, according to the partition layout, without any modification to the permanent wiring, and this system is described together with an extensive and intensive underfloor duct system with permanently wired floor socket outlets.The paper deals also with the electrical supplies to lifts and escalators, air-conditioning-plant rooms and special departments. Information is given on the clock system, various sound systems, alarms and security control and amenity and recreation areas such as restaurants, kitchens, underground garages, swimming pool and cinema/theatre etc. A brief description is given of the heating and air-conditioning plant, owing to the considerable quantity of electrical services employed.