This is the website of the LEO Computers Society, celebrating the World’s First Business Computer.

  • Dates for your diary. Events for 2022. Follow this link for further information - There will be another Zoom on Monday 24 January 2022 at 15:30 GMT. The topic is “Inside the LEO archive” and will be led by Luke Thorne, our Archivist at the Centre for Computing History at Cambridge. REUNION and LEO Exhibition: Sunday, 10th April 2022 . From midday at the Victory Services Club, Marble Arch, …

    Dates for your diary. Events for 2022. Follow this link for further information Read More »

  • LEO MOMENTS IN HISTORY - September 1951  – At J. Lyons & Co on Wednesday, 5th September 1951 the Bakery Valuations programme was run to completion on real data as an experiment to test the hardware.  As noted in Ernest Lenaerts notebook for that date it ran from 3:50 to 5:35 without a fault and was the longest run of any …


  • Zoom For LEO Computers Society Members - We are organizing a new series of Zoom Meetings. See Below Wednesday Online celebrations! During the past year we have discovered that online forums and presentations have been a great way to get our members together. Zoom has allowed former colleagues, now living in different continents to reminisce together and for, 22nd September 17.00 BST …

    Zoom For LEO Computers Society Members Read More »

  • Antiques Road Trip - The BBC programme Antiques Road Trip made a stop off at Cambridge to visit the Cambridge Computer History Museum and interviewed Jason Fitzpatrick the Museum founder. Jason covered many interesting topics including early calculators, EDSAC, LEO and the BBC Micro and ARM chips. You can hear and view the section from Cambridge Here
  • Presentation on J. Lyons and Company now on YouTube - The Presentation that Neville Lyons gave on the LEO Computers Society Zoom on 13 May 2021 is now on YouTube
  • 70th Anniversary - 2021 marks LEO’s 70th Anniversary Year – unfortunately the Trustees felt they had to postpone the Reunion from 2021 but replace it with a series of Zoom events to celebrate the events of 1951 (see the post on the new Zoom dates) The new date for the Reunion at the Victory Services Club is Sunday, …

    70th Anniversary Read More »

  • New Date for Reunion - There is a revised date for our Reunion –   Sunday, 10th April 2022. Details will follow

The Centre for Computing History, Cambridge is our partner in a National Lottery Heritage funded project Swiss Rolls, Tea and the Electronic Office. To find out more about this click (Welcome to LEO)
There is also a regular Project Blog at (Project Blog).
During the Covid Pandemic the Museum has had to close its doors. As it depends on school and individual visits for almost all its income, it has been appealing for donations. We hope that members may be able to help them in these difficult times. (See Here)

LEO Matters for Autumn/Winter 2020 has been published LEO Matters and Issue 71 of ICL All Stars from Australia.


It was, surprisingly, a British catering firm, J. Lyons and Co – famous for their teashops, Swiss rolls and ice cream which pioneered the development of computing for commercial applications. As Guinness World Records ratifies, Lyons Electronic Office (LEO) was the first business computer in the world.

In 1951 the LEO I computer was operational and ran the world’s first regular routine office computer job.

The LEO Computers Society (which has charitable status) started life as a reunion society for people who worked on these remarkable machines. Its principal mission now is to ensure that LEO’s heritage is preserved, protected and – importantly – promoted to wider audiences. Read more about the LEO Computer Societies mission (Our Mission). If you want to understand the development timeline and the rationale for its development see what the Science Museum has to say.
More About Us

URGENT REQUEST: Do you have any LEO memorabilia – e.g. pieces of hardware, engineering drawings, charts and plans, programming information, computer files, correspondence or reminiscences?
If so, you can help us. We are collecting such material to join a growing archive at the Centre for Computing History in Cambridge, our partners in a National Lottery Heritage funded project to preserve, protect and promote the history of the world’s first business computer.
Please contact the Secretary@leo-computers.org.uk for further details.


Become a member

Membership of the Society is open to:

  • all ex-employees of LEO Computers and its succeeding companies;
  • anyone who worked with a LEO computer;
  • and indeed anyone who has an interest in the history of LEO Computers.
  • we especially would encourage educators to join

We welcome the active participation of members – whether through volunteering as interviewers for oral histories, writing their own reminiscences, contributing to the newsletter or simply through spreading the word!

So Join Today