The Modern Records Centre holds the archives of the statistician John Simmons (1902-1985), including key material on the development of the pioneering LEO computers by J. Lyons & Company Ltd. during the 1940s and 1950s.

A selection of documents about the development of 'LEO I', the world's first business computer, have now been digitised and made available online:

	Electric machines: Report of a visit by Mr Booth and others to CambridgeLink opens in a new window	November 1947
	Report on payroll preparation by electronic computerLink opens in a new window	16 January 1948
	Site for electronic computer (memorandum)Link opens in a new window	29 November 1948
	Electronic computer (report no.1)Link opens in a new window	4 February 1949
	Development of the electronic calculating machine (report no.2)Link opens in a new window	8 April 1949
	Lyons electronic computer (report no.3)Link opens in a new window	23 May 1949
	The development of EDSAC (report)Link opens in a new window	23 May 1949
	Lyons Electronic Office (report no.4)Link opens in a new window	14 June 1949
	Lyons Electronic Office (report no.5)Link opens in a new window	31 August 1949
	The layman's guide to LEO (computer manual)Link opens in a new window	[1950?]
	LEO (report no.6)Link opens in a new window	31 January 1950
	Circulars relating to demonstration of LEOLink opens in a new window	2 March 1950
	Reactions to the demonstration of LEO on 7th and 8th March 1950Link opens in a new window	20 March 1950
	Notes on LEO and office managementLink opens in a new window	29-30 March 1950
	Notes on LEO and office managementLink opens in a new window	February-June 1950
	Visit of Lord Halsbury (memorandum)Link opens in a new window	1 May 1950
	LEO (report no.7)Link opens in a new window	3 July 1950
	LEO (report no.8)Link opens in a new window	11 December 1950
	LEO (memorandum)Link opens in a new window	2 April 1951
	Demonstration of LEO (notes for talk)Link opens in a new window	17 April 1951
	Menu for dinner to celebrate the successful demonstration of clerical work performed by the calculator of LEOLink opens in a new window	16 May 1951
	LEO (report no.9)Link opens in a new window	18 June 1951
	LEO (report)Link opens in a new window	22 February 1952
	Development of LEO to link with a line-a-time printer (memorandum)Link opens in a new window	17 June 1952
	Modifications to LEO to make it independent of Standard's equipment (report)Link opens in a new window	3 October 1952
	LEO (report no.10)Link opens in a new window	27 November 1952
	Future policy for LEO (memorandum)Link opens in a new window	19 June 1953
	Memorandum regarding near-completion of LEOLink opens in a new window	7 December 1953
	LEO: Lyons Electronic Office (promotional leaflet)Link opens in a new window	16 February 1954
	Menu for dinner to celebrate the inauguration of LEOLink opens in a new window	27 May 1954
	LEO (report no.11)Link opens in a new window	30 June 1954
	LEO chronicle 1947-1954Link opens in a new window	[1954?]
	Visit of T.R. Thompson and A.B. Barnes to the USA: General report to directorsLink opens in a new window	14 December 1955
	Photographs of LEOLink opens in a new window