The Company was founded in Manchester on the 12th November 1878 under the title of The Engine and Boiler Insurance Company with RB Longridge as Chairman and Michael Longridge (his nephew) as Chief Engineer. The Longridge family were established engineers at the beginning of the 19th Century. They were originally iron masters from Bedlington, Northumberland who also supplied castings and forgings. They were involved in the early development of industrial steam engines and were business partners with both George and Robert Stephenson. RB Longridge formed The Steam Boiler Assurance Company in 1859 but later resigned. Following his resignation, he formed The Engine and Boiler Insurance Company Limited. Within two years the name of the company was altered to The Engine, Boiler and Employers' Liability Company Limited. In 1903, its silver jubilee year, the title British Engine, Boiler and Electrical Insurance Company Limited was adopted until 1978 when the title was abbreviated to British Engine Insurance Limited. The family association with the company, was terminated in 1966 with the retirement of HM Longridge. The name of Longridge was perpetuated in the title of the Head Office building in Manchester- Longridge House, erected in 1959 on a site embracing that of the original Manchester Steam Users Association of which RB Longridge was Chief Inspector. Longridge House was demolished in 1997 due to the massive structural damage it sustained following the explosion of a bomb placed in a van, by the IRA, which had been parked outside the building. The Company Number was 14644, registered at Companies House in Scotland.

Associated Electrical Industries (AEI) was formed in 1928 as a financial holding company for a number of leading electrical manufacturing and trading companies in the United Kingdom. The two major constituent companies were British Thomson-Houston (BTH) based at Rugby, (Mill Road Works) and Metropolitan-Vickers Electrical Company Ltd (Metrovicks) situated at Trafford Park, Manchester. However, fierce rivalry existed between the Metrovick and BTH brands resulting in internal competition and duplicated management. This was highlighted during the Second World War in 1939, when Metrovicks and BTH became the first two firms in the world to construct jet engines (independently from each other). Following the Second World War, in 1954, AEI expanded to consist of BTH, Metrovicks, Edison Swan Electric Co, Ferguson Pailin, Hotpoint Electric Appliance Co, International Refrigerator Co, Newton Victor, Sunvic Controls, Premier Electric Heaters, Siemens Bros (1955) and Birlec (1954). In 1959 AEI decided to remove the familiar brands of BTH and Metrovicks and consolidate both as AEI resulting in internal problems and a fall in sales and market value. However, AEI acquired a variety of companies from 1959 to 1967, these included Associated Insulation Products, W. T. Henley’s Telegraph Works Co (1958), and London Electric Wire Co and Smiths (1958), Submarine Cables, Hackbridge Holdings Ltd., The Lancashire Dynamo and Crypto Ltd., W.T. Avery Ltd., Henley and Schreiber. The General Electric Company bought AEI in 1967.

Kennedy & Donkin was established in 1889 by Sir Alexander Kennedy as a consultant engineering practice focused on electrical engineering. In 1897 Sydney Bryan Donkin joined the business with Kennedy and Donkin becoming partners in 1908. In 1913 the firm become Kennedy and Donkin and the business went onto focus on power generation and electricity distribution projects. The firm acted as a consultant engineer to the Central Electricity Board for the construction of the National Grid in the 1930s. The company would later work on other large scale engineering projects such as the construction of the Aswan Dam, Egypt, in 1947 and on the Pimlico district heating scheme in 1949. In 1994 Kennedy and Donkin was acquired by WMX Technologies Incorporated and become Rust, Kennedy & Donkin. In 1998 the company was purchased by Parsons Brinckerhoff, becoming PB Kennedy and Donkin.