Siemens Brothers and Company Limited was an electrical engineering design and manufacturing business in London, England.

He found employment in Birmingham with engineers Fox, Henderson & Co and became a naturalised British subject in 1859, the same day as he married the daughter of an Edinburgh lawyer.

[9][note 4] Following his death shares were offered, somewhat unwillingly, to London manager Johann Carl Ludwig Loeffler (1831–1906) to retain his services.

He managed to increase his holding to 25% but there were disagreements as to how the firm was run and Alexander Siemens, William's adopted son, replaced Loeffler in 1888.

[5] Loeffler died in the Tyrol 18 years later leaving an estate in excess of £1.5 million, he was a prominent investor in West Australian mines.

[5] By 1900 Siemens Brothers had constructed and laid seven North Atlantic cables[8] In 1903, with Nuremberg's Elektrizitäts-Aktiengesellschaft vormals Schuckert & Co or E.-AG, they formed a new entity, Siemens-Schuckertwerke, to hold all their jointly-owned heavy-current operations.

[12] In 1908, Siemens Brothers Dynamo Works Limited opened a metal filament lamp factory in rented premises at Tyssen Street, Dalston, London.

[13] In 1919 its capacity was 2.5 million lamps per annum[14] but advances in technology left its products unwanted and the Dalston factory closed in 1923.

An L-shaped five-storey building, used for making rubber-coated copper-wire cable, was among the largest factories in London when built.

[17] Financier Charles Birch Crisp was leading a consortium of investors who were not connected with the electrical engineering industry.

[21] Siemens Brothers coverage of the whole field of telecommunications meant the volume and range of their wartime supply of cables and apparatus was enormous extending to the manufacture of radar equipment.

[23] One of the many critical components of World War II's Operation Overlord was to ensure a steady supply of fuel to the Allied forces.

Operation Pluto (PipeLine Under The Ocean) was facilitated by Mr A C Hartley, chief engineer of the Anglo-Iranian Oil Company, who suggested to Siemens Brothers that a submarine cable might be modified to carry petrol below the channel to France.

Siemens Brothers' experience with gas pressure cables lead to their design manufacture and trial (under the Thames) of what became PLUTO.

After the AEI take-over, the Woolwich factory principally produced Strowger telephone exchanges for the General Post Office.

Losing both the ordnance factory and the Siemens plant at roughly the same time caused large-scale unemployment in the area and decades of economic and social hardship.

[1] At the Woolwich site, which once covered thirty-five acres, several buildings testify of a rich industrial heritage.