Main image: Stan Evans, a newly recruited maintenance engineer, works on a LEO I circa 1956. Photograph courtesy of LEO Computers Society
By Hilary Caminer, Secretary of the LEO Computers Society.
In November 2026, LEO Computers Society, in conjunction with partners, is hosting a three-day 75th anniversary programme of events to coincide with the three days of LEO’s maiden run.
Seventy-five years ago from the date of this newsletter there was not one single computer anywhere in the world being used for business applications. That’s a very stark statement and one that we often forget.
Already in the late 1940s, the giant catering firm J Lyons & Co realised that the way forward for office work was to use electronic means. The Board of Lyons collaborated with scientists at Cambridge University to develop a computer derived from their EDSAC (Electronic Delay Storage Automatic Calculator) machine that was suitable for Lyons’ needs. EDSAC was built for scientific purposes and what developed was LEO – Lyons Electronic Office – designed to manage the myriad of daily back office calculations needed to run a huge company.
And so, in the final days of November 1951, LEO got to work calculating weekly bakery valuations, an event acknowledged by Guinness World Records as the very first run of a business computer.
The LEO Computers Society’s mission is to preserve and promote LEO’s heritage and its significant contribution to computer history and the charity has developed the following anniversary programme to celebrate this significant milestone.
November 2026 Anniversary programme:
• Saturday 28: The Centre for Computing History, Cambridge will host a programme of LEO-themed events including with a recreation of a Lyons teashop with their famous Nippy waitresses, a screening of the LEO film and family-focussed educational activities based around the Virtual LEO I and our LEO exhibits.
• Sunday 29: The National Museum of Computing at Bletchley Park will host a day of LEO-themed activities. Enjoy full museum access, see historic videos highlighting the women who built LEO, dive into hands-on family STEM challenges with the LEO 75th Anniversary Puzzle Book and hear from special guest speakers throughout the day!
• Monday 30: The Worshipful Company of Information Technologists, London will host a seminar day of presentations and discussion about LEO, looking at how the world’s first business computer influenced the way business computing developed, leading right up to today’s AI.
Get involved
If you have any suggestions about what we should include on these days or if you have any LEO memories – or even artefacts – please do get in touch with us at [email protected]
Alternatively, if you would like to be kept informed of the details of these celebratory events – including how to register – please send an email headed ‘75th Anniversary’ to Mike Storey – [email protected]
We hope very much that you will be able to join in this ‘festival of LEO’.