LEO Computers Limited was founded by J. Lyons and Co, a major catering and food manufacturing company, in 1954 in order to produce LEO II computers.

These computers had been developed following a trip by two of Lyon's managers to the United States of America to study management techniques. During this visit they were made aware of work being undertaken on electronic computers both there and at Cambridge University. Following their return they convinced the board to fund the Cambridge project, who were working on the EDSAC computer, before producing a design themselves. This design, which built upon the work done Cambridge, was named Lyons Electronic Office (LEO) and began operating in 1951. Initially it was used for valuation work but this would be later expanded to payroll and inventory. A second design, LEO II, was introduced in 1954 and due to interest from other companies a new company was formed to produce them, LEO Computers Limited. This was responsible to a range of bureau service as well as the supply of machines. In 1961 a third model, LEO III was introduced.

During the 1960s Lyons began to suffer financial difficulties and in 1963 LEO Computers was merged into a joint venture with English Electric, known as English Electric LEO Company. Lyons sold their stake in this new company to English Electric in 1964 which made it a wholly owned subsidiary of the latter company. It was then merged with the Marconi Company's computer interests, to form English Electric-Leo-Marconi Computers, before this was merged with Elliott Automation to form English Electric Computers Ltd. In 1968 this was taken over by International Computers and Tabulators to form International Computers Limited, which would be later acquired by Fujistu.