LEO- Lyons Electronic Office - was the worlds first purely business computer. Unusually for a computer system, LEO was developed out of a perceived business need by Joseph Lyons and Co. in the early 1950s. LEO was developed with assistance from Cambridge University and used techniques developed from the early scientific computer systems, mostly based at academic institutions many being purely experimental. Manchester University was another site where computing was being developed, albeit in an experimental way. It is hard to imagine today, with every home owning at least one computer system either in a PC, video recorder, teletext-equipped TV or even in the family car looking after fuel and emissions that when LEO was being developed the number of computers in the UK could be counted on less than the fingers of one hand...
LEO was developed from the first Lyons machine at Cadby Hall in London into a range of general of general purpose business computers known as the LEO III - there were two models, the 326 and the 360. The faster of the two was the 326. The LEO III models were introduced around 1961 and were very long lived, the last two models being decommissioned in Bristol and Cardiff in 1981. I was involved in decommissioning the Bristol machine, LEO III-70 which was a 326 model. Prior to decommissioning I had been employed as a systems engineer to provide engineering support for this machine. I had been trained at Charles House which was a BT (formerly GPO) installation, as was Bristol and Cardiff. I was unaware that the guys who were training me had been at the forefront of computer science in the 1950s. Many of the concepts embodied in LEO are to be found in today's PCs - multi-channel DMA for example, though LEO's version of a DMA controller was called an "assembler" - a term guranteed to cause confusion in onversation with programmers. LEO III had the the world's first multitasking operating system, called rather quaintly "the master routine". It also had a microprogrammed CPU - a very advanced idea at the time. LEO was beautifully made and all those engineers who worked on LEO were very proud to have been connected with the machine and we were very sad when we switched it off for the last time. I and (I think) six other colleagues were the last generation of engineers recruited by ICL to work on LEO and I joined the company last of all, several weeks after the others in January 1980. I have to say that much of what I learned during this period has underpinned my entire understanding of computers and it was a marvelous opportunity for a young engineer to have experienced what some have called "the golden age of computing"
More about LEO can be found at http://www.leo-computers.org.uk
and here is a fascinating account of home computing in the 1970s