Many changes have occurred since the fortress was first reopened as a military museum. Its shore batteries, armouries and barracks have been restored, there is a 10th Light Horse display and trails to a collection of naval guns and torpedoes.

The fortress is also home to the SE Asia, US Submariners and Merchant Navy Memorials.

Museum curator David Theodore said Sunday’s celebration featuring other displays including military vehicles would give locals the chance to revisit the forts.

He said many myths about what had been constructed at the forts had been debunked by staff and volunteers.

One was that many people thought there were tunnels which connected areas within the fort and beyond.

“That’s just not true,” he said. “These rumours still persist, but they were discounted years ago.”

Tunnels do exist but they provide access to magazines where cordite and shells were stored in a controlled temperature.

The main magazine was created with a horseshoe-shaped tunnel around the storage to provide access for soldiers.

The fortress was opened in 1893 as the first federal defence facility to be funded by all Australian States. From 1893 to 1956 the guns of King George Sound maintained their role as a deterrent, though never fired a shot in anger.

The barracks housed a small permanent garrison to man the guns.

It was revamped and turned into a museum by 1990.