The D-Day headquarters used during the Second World War has opened its doors inviting veterans and personnel to look around.
Southwick House sits in the Hampshire countryside.
It is where General Eisenhower and Field Marshal Montgomery, together with Admiral Ramsay - commander of the Allied Naval Expeditionary Force - planned Operations Overlord and Neptune.
The date for D-Day was set there 75 years ago.
Historian and retired Colonel Jeremy Green said the building in the run-up to D-Day was "probably the most important place in Europe".
Southwick House is now used by the Defence School of Policing and Guarding, but still has the map room inside.
The D-Day landings onto the beaches in Normandy were originally scheduled for 5 June 1944 – but in true British fashion, the weather had other ideas.
Although US meteorologists believed conditions would be suitable, British scientist James Stagg thought otherwise.
Mr Stagg managed to convince commanders to delay the operation by 24 hours, and hold out for better weather - it was the right call.
RAF meteorologist Flight Lieutenant Mark Bevan said "it is very hard to imagine" the "huge pressure" meteorologists were put under to accurately forecast the weather.
A framed letter from General Eisenhower hangs on the wall, with the words "I thank the lord we went when we did".
However, the weather was only half the battle for those landing on the Normandy beaches on 6 June 1944.
"An acoustic mine went off and we were sinking very slowly - [it] took about three or four hours for us to sink," said D-Day veteran Ron Smith.
"Anybody who said they wasn't frightened is lying...luckily I was well protected by the wheelhouse but three people died onboard."
With the 75th anniversary of that day approaching, many will return to Normandy in June to remember the realities of the events that were planned at Southwick House.