Long after the war, in the 1970s, the secret site was abandoned and buried under soil.
The rooms are open to visitors as they were discovered nine years ago, with wartime graffiti, peeling paint on the walls and visible pipes and ducts.
Volunteers who researched Fan Bay and helped open the plotting rooms to the public have also uncovered the personal stories of those who served at the site.
Gordon Wise, a White Cliffs of Dover volunteer, said of the discovery: “A name in a service record, or a detail in a photograph, helps connect the surviving marks on the walls with someone’s working day.
“There are still questions to answer, but each discovery helps us build a clearer picture of the people behind the machinery.”