This extraordinary and very secret part of Britain’s history was originally created by Henry VIII to build the navy upon which Britain depended. As new wars were fought, and new technologies developed, the Arsenal grew. It eventually became a secret city inside London with its own railway, hospital, school and everything else the thousands of workers and their families might need. Taking a guided tour is a must.
https://www.armymuseums.org.
Look at http://www.royal-arsenal-