L McMichael Limited was formed in 1920 by Hubert Leslie McMichael (1884-1951). In 1919, he had started a business dealing in 'war surplus' radio equipment to supply the growing needs of wireless experimenters which operated from his home in Hampstead. In mid 1920, he decided to pursue this business, establishing L McMichael Limited in Slough. He, along with his friend from the London Wireless Club, René Henri Klein, became its directors. At the same time, another business headed by Benjamin Hesketh was established that specialised in the manufacture of wireless components and instruments of his own novel and advanced design. By mid 1921, L McMichael Limited was marketing the wireless components and instruments manufacturerd by Hesketh and then in 1922, both companies were completely integrated, adopting the trademark MH (McMichael Hesketh).

The company was established at an ideal time due to the beginning of the broadcasting era in 1922 and the creation of the British Broadcasting Company (BBC). L McMichael Limited began designing for the broadcast listener as well as the broadcast experimenter, releasing their first broadcast receivers in 1923.

In 1926, L McMichael Limited became a Government Contractor supplying wireless sets to the Royal Navy, and in 1928 they also manufactured two experiemental cathode ray direction finders for the US Navy.

The company was continuously expanding facilities so that, by 1930, they were designing and producing every class of radio component and associated device with the exceptions of thermionic valves and headphones. Until the mid 1930s, the company was also working with Robert Watson-Watt exploring cathode ray direction finding and ionosphere measurements using pulse emissions. Some secrecy surrounded these works but these explorations led them to establish the foundations of Radar. These works eventually became public through the creation of McMichael Radio Limited in 1932. From 1936, the company also began small scale television receiver production, although this was halted with the outbreak of the Second World War in 1939.

During the Second World War, the company was involved in a variety of engineering production. They focused on light electrical and light mechanical engineering, radio communications, radar communications, IFF equipment and magnetic mine detection and detonation. Following the war, they recommenced production of domestic radio and television receivers, but also continued with military work, producing items such as sonar buoys.

In 1956, the company merged with Sobel Group to become Radio and Allied Industries Ltd. They continued with domestic radio and television production under the Sobel name and military equipment under the McMichael Radio Ltd name. In 1960, they produced equipment for the British satelite UK1.

In 1961, Radio and Allied Industries Ltd was bought out by GEC and McMichael Radio Ltd operated as an autonomous subsiduary of GEC. Then in 1963, McMichael Radio Ltd changed its name to McMichael Ltd due to no longer being active in the field of domestic radio.

In 1982, McMichael Ltd changed its name again to Gecophone Ltd and in 1988, they became part of GEC Power Systems Ltd, then of GEC Alsthom in 1989.