Multiple units are the unsung heroes of the modern railway system. Although they make up the main form of rolling stock for the majority of rail passenger services operated worldwide, particularly in high-density inner-city and urban traffic, they see much less media coverage than the more popular locomotive types. The many advantages of these units, as opposed to locomotive-hauled trains, include higher capacity, less track damage and lower operating costs, making them an ever more popular choice for modern, cost-conscious railway operators in Great Britain and around the world. Illustrated with more than 180 photographs, this book details the history of the major unit types that have operated on the UK's rail network, beginning with the earliest Victorian-era steam railcars and the first late-Victorian experiments with electric-powered traction, and going right up to the modern hybrid-powered multiple units currently under development. The story is told through a selection of photographs, class details and tables listing the major unit types classified by propulsion method and generation. 180 illustrations