Plessey: The Tube’s secret wartime underground factory
Introduction
During the Second World War, the Plessey defence electronics company built a secret factory in newly constructed Underground tunnels at the eastern end of the Central line. The tunnels were part of an extension interrupted by the outbreak of war in 1939.
Plessey’s factory in Ilford in Essex was heavily bombed in September and October 1940 during the Blitz. With the equipment manufactured by Plessey vital for the war effort, a new location was needed that offered relative safety from air raids. The incomplete Central line tunnels were quickly identified as ideal and conversion began.
The factory
Construction of the underground Plessey factory began in late 1940 in the 2.5-mile-long twin tunnels between Leytonstone and Gants Hill. Construction was staggered so that workers were able to begin manufacturing components in 1941. By March 1942 the factory was fully complete with flat floors, electrical switch rooms and air-conditioning installed in the Central line tunnels. In total, the factory took 16 months to complete.
The workforce
The wartime factory had 2,000 staff, mostly women, working in shifts 24 hours a day. They could enter and exit the factory at Gants Hill, Redbridge or Wanstead. Plessey produced a variety of vital defence electronics equipment, including the wireless receivers used in the cockpits of bomber aircraft. The work could be repetitive and tiring, particularly with the lack of natural light underground. But this also meant work could continue safely around the clock.
A railway within a railway
One of the most vital aspects of the conversion of the Tube tunnels to factory use was the installation of a miniature gauge railway. Battery locomotives pulled along small carriages to ferry raw materials and completed components along the tunnels.
Return to normality
The Plessey underground factory closed at the end of the Second World War in 1945. The factory and its workforce had provided a vital wartime contribution, enabled by the alternative use of unfinished Tube tunnels. Despite difficult post-war economic conditions, the Central line extension was completed and finally opened in 1947. This film marks the occasion, including footage of the Plessey factory during the war years.
This content, including several other objects, can be seen in the Hidden London exhibition at the Museum
