The LEO (Lyons Electronic Office) was a series of early computer systems created by J. Lyons and Co. The first in the series, the LEO I, was the first computer used for commercial business applications.
The prototype LEO I was modelled closely on the Cambridge EDSAC. Its construction was overseen by Oliver Standingford, Raymond Thompson and David Caminer of J. Lyons and Co. LEO I ran its first business application in 1951. In 1954 Lyons formed LEO Computers Ltd to market LEO I and its successors LEO II and LEO III to other companies. LEO Computers eventually became part of English Electric Company (EEL), (EELM), then English Electric Computers (EEC), where the same team developed the faster LEO 360 and even faster LEO 326 models. It then passed to International Computers Limited (ICL) and ultimately Fujitsu.
LEO series computers were still in use until 1981.
Origins and initial design
J. Lyons and Co. was one of the UK's leading catering and fo