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of Woodfield Works, Harrow Road, London: of Acton Lane Works, Chiswick, London, W4. Telephone: Chiswick 1370. Telegraphic Address: "Megger, Chisk, London". (1937)
1903 Company moved from Westbourne Park to Acton Lane, near Acton Green.
1903 trademark registered for Megger tester
c.1906 Developed chart recorder.
1910 Developed electrical testing apparatus for water purity.
1914 Electrical engineers. Manufacturers of electrical instruments, portable instruments for measuring resistance, signalling systems for ships, especially men-of-war. Employees 350 to 400. 
WWI. They made steering and target equipment for the Royal Navy during the First World War.
Post-WWI. Extended their site.
1920 January - Physical and Optical Societies Exhibition. Exhibitor of electrical instruments. Also Dionic water tester. 
1922 Producing apparatus for "distant indication" which proved so successful that a separate division was established.
1923 The first chairman of Evershed and Vignoles was the late Professor W. E. Ayrton who held the position till within a few months of his death in 1908. Since that date, the chairmanship had remained vacant. Mr Sydney Evershed, who recently retired from the position of managing director of the company, accepted the office of chairman, and in addition acted as consultant to the company. Mr E. B. Vignoles and Mr A. Vines remained managing directors of the company.
Late 1920s. Employed approximately 500.
1931 W. A. Vignoles was appointed M.D..
1931 Midworth Distant Repeater
1937 Electrical and mechanical engineers. 
1937 Listed Exhibitor - British Industries Fair. Sole manufacturers of "Megger" Insulation Testers, Earth Resistance Tester, Capacity Meters, and Dionic Water Testers. Electrical Indicating and Recording Instruments. Remote Indication and Control Apparatus, Electrical Tachometers, and Marine Instruments. 
WWII. Numbers rose to over 1,000 in the Second World War, when aircraft instruments were also made.
Early 1960s Over 1,500 employees.
1961 Manufacturers of electrical testing equipment. 1,870 employees. 
1971 George Kent sold much of the company to Thorn Electrical Industries. The company was mainly involved in making defence electronic equipment at Acton Lane. Several senior members of the board resigned and were replaced by directors of Avo and Taylor Electrical Instruments, also owned by Thorn
1980 c.450 people were employed at Acton Lane.
c.1986 Evershed and Vignoles was taken over by Avo Ltd, of Avocet House, 92-96 Vauxhall Bridge Road, London, SW1, another member of the Thorn EMI group. The Acton Lane works closed down at about that time.
1987 the name of the company was changed to Megger Instruments Limited.
By 1988 Evershed and Vignoles was part of Meggitt Holdings