The Telegraph | Dec 5, 2012
In April 1944 the fort was used by King George VI, Churchill and Eisenhower along with General Bernard Montgomery and Acting Admiral Louis Mountbatten to watch the exercise.
The group watched a demonstration of carpet bombing followed by an assault landing by troops.
The use of live ammunition in a rehearsal run was not regular practice, but military leaders wanted it to be as realistic as possible for the soldiers.
Built in 1943, the fort was a specially constructed concrete bunker and observation post. It was 90 feet long with walls, floor and ceiling all three feet thick, and was considered a safe place for the group to witness the rehearsal of the Normandy landings.
Visitors can now go inside the bunker and look through the same observation slit the men used to view the training exercise.