The latest in our series of early technologies from Michael Bennett-Levy’s collection looks at the world’s first commercial business computer, the LEO II/3. The LEO II (short for Lyons Electronic Office) was the successor to the LEO I, which was designed by Oliver Standingford and Raymond Thompson of J. Lyons and Co. – one of the UK’s leading catering and food manufacturing companies in the first half of the 20th century.

The LEO I ran its first business application in 1951 and its tasks included valuation jobs, payroll and inventory for J.Lyons and Co. It was built after Standingford and Thompson met Herman Goldstine, one of the original developers of the first general-purpose electronic computer, ENIAC, during a visit to the US in 1947. They quickly recognized the potential of computers in the administration of a major business enterprise and on learning that another such machine called EDSAC was being built at Cambridge they visited the University upon their arrival back in the UK. Following the successful completion of EDSAC in 1949 the Lyon’s board agreed to start construction of their own machine, expanding on the EDSAC design.

The result was LEO I, which began operating in 1951 boasting a clock speed of 500 kHz and its ultrasonic delay line memory based on tanks of mercury, with 2K (2048) 35-bit words was four times as large as that of EDSAC. Its multiple input/output buffers were initially linked to fast paper tape readers and punches, fast punched card readers and punches, and a 100 line a minute tabulator. Later other devices including magnetic tape were added.

The success of the LEO I led to the creation of the LEO II. The first Leo II/1 replaced Lyons’ LEO I computer, while LEO II/2 was sold to the Will Tobacco Co., LEO II/3 went to steel company Stuart and Lloyds and Leo II/4 was sold to the Ford Motor Co. UK. Although Wills Tobacco Co. took delivery of LEO II/2 before Stuart and Lloyds’ LEO II/3, it wasn’t turned on until two months after LEO II/3, which was switched on in May, 1958. If the world’s first commercial computer is defined as the first computer sold and used by a company for commercial work then Stuart and Lloyds’ LEO II/3 can lay claim to that title.

Parts from LEO II/3 that went to auction at Bonhams Knightsbridge last year included:

  • Tape head reader unit, with split part operation and monitor controls for 'run' and 'halt', blue-painted faceplate and chrome removing pull;
  • Memory carriage unit, with 11-valve lineup (one missing, one vacuum loss), rectangular chassis with resistor boards below and rack hoops at each end;
  • Frequency Monitor Unit with CRT display, with square chassis and vision mixer valves on top, used in conjunction with the delay tube box;
  • CRT tube from the main control console, one of three tubes from the desk, (vacuum lost, gun end cracked);
  • A LEO magnetic tube drum, lockable lids and the tape protected in reel core;
  • A series of circuit diagram blueprints covering the magnetic drum reader, amplifier, storage and input circuits;
  • Two punch cards, both processed by LEOII/3, showing punched number columns;
  • Newspapers covering the installation of LEO II/3 in 1957 and its eventual decommissioning in 1971;
  • The framed final farewell message printed out from LEO II/3.
  • Michael Bennett-Levy gives a brief overview of the history of LEO II/3 in the video below.