The following pictures have been very kindly provided by Phil Courtney and I would like to say a big thank you to him and for his support; see emails page.

The longest, narrowest factory ever; five miles long and twelve feet wide!

London Illustrated News, December 6th 1947

Plessey Underground Factory

The official opening by the Minister of Transport of a section of the Eastern Extension of the Central Line (London Transport Passenger Board) between Leytonstone and Gants Hill (Ilford), which has been arranged for December 12, will bring back many memories to thousands of workpeople and reveal to a much larger public an interesting story of wartime improvisation. This tunnel was almost complete when the outbreak of war suspended operations and in 1942, as our diagrammatic drawing shows, it was converted and used by the Plessey Company, Ltd., of Ilford, for the manufacture of aircraft components, radio and associated equipment for war purposes; and an air-conditioned under-ground factory (of somewhat unconventional shape and site) was laid out in nearly five miles of running tunnel (single 12-ft-diameter tube), and, with the addition of three stations (at Wanstead, Redbridge and Gants Hill), comprised a total floor space of 300,000 sq. ft.
Intermediate points of entry at Cambridge park and Danehurst Gardens were constructed, so that no one had to walk more than a quarter of a mile to work and lifts were installed at these two points, while at the stations the normal escalators were in use. A miniature railway (illustrated in one of the insets) of 18-in. gauge extended throughout the tunnels for the transport of raw materials, finished components, and, in cases of necessity, for passengers. Many thousands of tons of concrete were used to provide the factory floor, which was laid in such a position as at once to give maximum floor space without restricting head-room, and also to provide space beneath for the distribution of conditioned air and the extraction of foul air. The factory was completed in March 1942 and was in use until 1946.
During these four years the works operated day and night and the number of workers at the peak period was about 4000. The stations were used for offices, stores and first aid, and emergency flood-gates were constructed in the tunnel below the River Roding, in case aerial bombing should cause any infiltration of the water into the tunnel. Many millions of components were produced, among them being aircraft pumps, cartridge engine starters and breeches, aircraft wiring components, radio components, magnetos, field telephones, gear-cutting tools, gear levers and other components for armoured cars, shell fuses and so forth.

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