LEO computers: Ernest Lenaerts Papers

Scope and Content

A small collection of papers of the computer engineer Ernest Lenaerts, who played an important role in the development of the LEO computer. The collection includes Lenaerts' correspondence with Lyons colleagues about his work on the EDSAC and subsequent development of LEO I (ELH/1), as well as the notes he compiled on the EDSAC (ELH/2). There are also various reports, memoranda and patents which relate to Lenaerts work with LEO Computers and English Electric LEO Marconi.

Administrative / Biographical History

Ernest Lenaerts was born in 1910 and educated in London. He joined J Lyons and Co in 1926, and worked in their statistical office. During the Second World War he was a RAF wireless mechanic, and worked on radio countermeasures in London. Lenaerts' wartime experience with electronics encouraged him to apply for a post in J Lyons' Electrical Research Department after the war. This coincided with the company's interest in using computers to automate office procedures. Lenaerts was sent to work with Maurice Wilkes at the Mathematical Laboratory in Cambridge where the EDSAC computer was being developed. Here he acquired the expertise which would be put to use in developing Lyons' own computer LEO I (Lyons Electronic Office), on which he worked with John Pinkerton between 1949-1953. Lenaerts made important contributions to its data input and output systems. He later worked on the further versions of LEO, after LEO Computers Ltd. had been established as an independent company to develop the computer commercially. He was LEO's field research manager between 1959 and 1963, responsible for dealing with the maintenance of LEO computers.

When LEO merged with English Electric in 1963, Lenaerts became manager of its measurements laboratory. In his later work Lenaerts became interested in human interactions with computers and did work on speech recognition, and on dealing with computer noise. He also researched ways of counteracting static charges produced by fast-moving computer paper tapes. Lenaerts retired in 1969, and died in 1997.

Conditions Governing Access

The collection is open to any accredited reader.

The collection includes material which is subject to the Data Protection Act 1998. Under Section 33 of the Data Protection Act 1998 (DPA), The University of Manchester Library (UML) holds the right to process personal data for research purposes. The Data Protection (Processing of Sensitive Personal Data) Order 2000 enables the UML to process sensitive personal data for research purposes. In accordance with the DPA, UML has made every attempt to ensure that all personal and sensitive personal data has been processed fairly, lawfully and accurately. Users of the archive are expected to comply with the Data Protection Act 1998, and will be required to sign a form acknowledging that they will abide by the requirements of the Act in any further processing of the material by themselves.

Open parts of this collection, and the catalogue descriptions, may contain personal data about living individuals. Some items in this collection may be closed to public inspection in line with the requirements of the DPA. Restrictions/closures of specific items will be indicated in the catalogue.

Acquisition Information

It is believed that the collection was transferred to the NAHC through the offices of Professor Martin Campbell-Kelly (University of Warwick) following Lenaerts death in 1996.

Separated Material

Some of Lenaert's notebooks are believed to be in the custody of the LEO Computers History Society.

Conditions Governing Use

Photocopies and photographic copies of material in the archive can be supplied for private study purposes only, depending on the condition of the documents.

A number of items within the archive remain within copyright under the terms of the Copyright, Designs and Patents Act 1988; it is the responsibility of users to obtain the copyright holder's permission for reproduction of copyright material for purposes other than research or private study.

Prior written permission must be obtained from the Library for publication or reproduction of any material within the archive. Please contact the Head of Special Collections, John Rylands Library, 150 Deansgate, Manchester, M3 3EH.


Accruals are possible.

Related Material

The Lenaerts papers are on of several LEO-related collections held by the Library as part of its History of Computing Collection. These include the main LEO archive (NAHC LEO) and the papers of John Pinkerton, a former colleague of Lenaerts.

Papers of John Simmons, a LEO executive, with whom Lenaerts worked are held by the Modern Records Office, University of Warwick.


The LEO Computers Society contains a good deal of information on the history of the company and its computers. P.J. Bird, LEO: the first business computer (Wokingham, 1994) is a history of the company. Georgina Ferry, A computer called LEO: Lyons tea shops and the world's first office computer, London: Fourth Estate 2003; D. T. Caminer, J.B.B. Aris, P.M.R. Hermon, F.F. Land, User-Driven innovation: the world's first business computer (London: McGraw-Hill 1996).