Elliott Brother (London) Ltd. has its origins with William Elliott who established a business in Tash Street, Gray's Inn as a maker of drawing instruments (after serving an apprenticeship). By 1807 he had moved to a shop and workshop in High Holborn, and by 1816 he was manufacturing such items as telescopes and barometers. In 1830 he moved to 56, Strand and took his sons, Frederick Henry Elliott and Charles Alfred Elliott, into partnership. The company began to manufacture instruments for surveying, for railways (e.g. steam pressure indicators) and scientific instruments of all kinds.

William Elliott died in 1853 and his sons continued the business as Elliott Bros. In 1865 Charles Elliott retired and he died in 1877. Frederick continued to run the business as sole proprietor and on his death in 1873 he left the business to his wife Susan. In the second half of the 19th century the company began manufacturing electrical instruments, and in 1893 they amalgamated with Theiler & Co, telegraph and instrument makers. In 1900 the company moved to new premises: Century Works, Connington Road, Lewisham. They began making speedometers, and instruments for ships and aircraft.

On 21 June 1916 a new company was formed in order to take over the business of William Oliver Smith, Willoughby Statham Smith, George Keith Buller Liphinstone and Laurence Willoughby Smith, which was trading as Elliott Brothers. This was to be known as Elliott Brothers (London) Limited and took over the assets of the previous company and continued to produce instruments for a variety of scientific, mathematical and industrial use.

During the interwar period Elliott Brothers (London) Limited continued to produce both electrical and mechanical instruments. From 1920 Siemens Brothers would enter into a working arrangement with the company to coordinate the design and manufacturing of the two. As part of this Siemens took a share of Elliotts, which would later become a controlling interest in the company. They would also transferrer their telegraph section to the company on 1st May 1925. The association of these two companies would not have entirely beneficial consequences for Elliotts, with the financial control that was exerted on the company being later described as a millstone around its neck and result in the company being starved of capital. As a result, the Lewisham factory was seen by many at the time as a technical backwater that had been by passed by the wartime contracts for RADAR and other electronic instruments. This situation continued until 1945 when the merchant bank Higginsons agreed to purchase the Siemens holding in the company, installing Geoffrey Lee as Managing Director.

Partly due to the company’s longstanding relation with the Admiralty, it had produced fire-control systems for Royal Navy warships from 1908, and partly due a series of unproductive discussion between the navy and Vickers-Armstrong, as well as several other engineering companies, 1946 would see the establishment of a institution that would reserve the fortunes of Elliott Brothers (London) Limited. At the time there was practically no electronics activity at the company’s existing factory and the Admiralty was well aware of the firm’s declining performance during the war but never the less it agreed to enter into discussion to allow the company to host a new research team to work on the MSR5 Medium Range Fire-Control System. As a result of these discussions it was agreed that, with the help of the Admiralty, Elliotts would establish a new research laboratory at a shadow factory site in Borehamwood, which was to be modelled on the existing General Electric Company’s Hirst Research Centre. Although this site started with on 45 employees it would later become the centre of the company’s computer research, and in 1994 would replace the Wembley site it was based on when GEC moved the Hirst Centre there.

In mid-1950 the first Elliott Brothers digital computer, the 152, made its first calculation. This had been developed as part of the Admiralty MSR5 project, with work continuing on the computer even after this had been cancelled. This initial work was followed by the development of several other models at the Borehamwood site including the 401 in 1953; TRIDAC, an analogue missile simulator delivered to the Royal Aircraft Establishment in 1954; the 153 and 311, both of which were produced for GCHQ; the 403, which was used at the Woomera test range, and the 405, which entered production in 1956 as the company’s first machine aimed at business and commercial applications, as opposed to scientific or research.

In 1947 the company merged with the weighing machine manufacturers B and P Swift. In 1950 it established a subsidiary known as Elliottronic Limited in order to exploit the newly developed printed circuit technology. In 1953 an Aviation Division was formed at Borehamwood; this formed the basis for Elliott Aviation and would begin work on a three-axis auto stabilisation system for the English Electric Lightning fighter aircraft. The following year in 1954 Elliott Brothers acquired Bristol's Instrument Co. to strengthen its process control activities.

In 1957 the former subsidiary, Elliottronic Limited, was reformed as a holding company and renamed Elliott-Automation Limited. In this new form the company would bring about the merger of Elliott Brothers (London) Limited and Associated Automation by acquiring the shares of these two companies in exchange for its own. This deal was accepted in early October 1957 and created the largest automation and instrument organisation in Europe at the time with both Elliott Brothers and Associated Automation becoming subsidiaries. The board of the new company was headed by Rudolph De Trafford with Loan Bagrit as deputy and managing director.

By 1959 the company had developed a new model of computer that made use of transitors to enable it to be of a much smaller size than previous machines had been. This was the 803 and approximately 211 of these were produced. These were some of the first non-defence related computers produced by the company and had a wide range of applications, from universities to power stations and distilleries to post offices.

By May 1965 the company was composed of seven subsidiary groups. These were the Microelectronics Group, which was made up of a sales; a modular circuits and an integrated circuits division as well as a research laboratory, the Electrical Measurements Division, which was made up of a servo components and a precision potentiometer division, E-A Space and Advanced Military Systems Ltd, Elliott Marine Automation Ltd, which was made up of a Marine Systems, a Marine Equipment and a Marine Service division, Elliott Traffic Automation Ltd, Elliott Electronic Tubes Ltd, which was made up of a Telecommunications and a Radar and Communications Instruments Division and the Automation Services Group, which was made up of E-A Technical Services Ltd and Elliott-Automation Services Ltd.

In 1967 the Elliott Automation group was merged into English Electric, becoming a subsidiary of the larger company. Despite this Elliott Brother (London) Limited was little changed, remained part of the E-A group. In 1968 EE itself was merged with the General Electric Company. This would bring about some restructuring as by 1974 Elliott Brothers, although still part of E-A, was only composed of three subsidiaries, EASAMS Ltd, ESAMS (Malaysia) Ltd and E.A. Industrial Corporation, as opposed to the seven that had made it up ten years previously. This would continue until 1982 when it became Marconi Avionics Limited.