The Royal Arsenal: Woolwich's 'secret city' of WW1
26 February 2014 Last updated at 02:04 GMT
Already a large gun and ammunitions manufacturing site before 1914, the Royal Arsenal in Woolwich expanded into a multitude of factories servicing the World War One war effort.
The huge site had its own internal railway system, employed 80,000 workers and has been described as the "secret city" of Woolwich, in south-east London.
Historian Ian Bull explained its importance to BBC London News. Find out more about WWI at Home on BBC London 94.9.