The Imperial War Museum was a settlement for the kids in The Enemy series, primarily used in The Dead, and was run by Jordan Hordern before it was abandoned during the fire that burned most of South London towards the end of The Dead.
It is noted as one of the only settlements in the South of London that had a group of kids living and surviving there. It is unknown if there were other settlements around them or if they were the only one, although this is unlikely as during The Dead it was mentioned that there were many kids running away from the fire and towards Lambeth Bridge who were not part of the Imperial War Museum Crew.
After the fire that burned down most of South London, the Imperial War Museum was left abandoned for most of the series until The End when a group of kids sent by Jordan arrived to take whatever weapons that survived the fire that could be used against the grown-ups in the Battle of Hyde Park.