Section of the mains electricity cable used to connect the Grosvenor Galleries to the Deptford substation. Made by Sebastian Ziani de Ferranti around 1890.

Sebastian Ziani de Ferranti’s design for high-voltage underground mains cables became the global standard. Existing cables could not handle the 10,000-volt current generated by Ferranti’s Deptford Power Station. Ferranti developed paper-insulated cables with conductors arranged in circles around a shared centre. Layers of waxed paper separated the outer earthed conductor from the inner live conductor.