This volume of a multi-volume set on English Computer Systems examines the major pioneering efforts in England during the period from the late 1950s until the late 1970s. These three firms – English Electric, Elliott Automation, and Lyons Electric – disappeared through mergers as the computer industry consolidated through government intervention. Each of these firms contributed innovative hardware and software architectural concepts to computing in England and around the world, such as stack-based machines, time-sharing, and multiprogramming as well as advances in programming languages. LEO I was the first business computer used to support business operations, yet it did not arise from academia or a commercial electronics company, but from a Tea Shoppe!