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HomeLifestyleManly's once secret underground tunnels

Manly’s once secret underground tunnels

Strolling through the native flora and fauna at North Head Sanctuary is an immersive treat, but many are unaware of what modern history lurks beneath.

Harbour Trust volunteers have spent two years revitalising the Close Defence Battery Observation Post and its sister facility, the Battery Observation Post – facilities that formed part of Fortress Sydney, a network of batteries (big guns) spanning 300 km of coastline during WWII. Connecting the North Head posts are a series of tunnels that visitors can experience while chaperoned.

Depression range finder inside the Observation Post.

The specialist volunteers, including ex-service people, carefully restored the historic sites to ensure they faithfully resembled their former configuration from almost 90 years ago.

Harbour Trust volunteer, Peter Lawrence, says the restoration of these areas is crucial for education.

“This is going to be used for historical reference and for education, so that people can come and see what happened 90 years ago. But it’s also an integral part of the heritage of North Head,” he says.

Interior of the Battery Observation Post, 1944. Photo credit: Courtesy of the Australian War Memorial

Restoration of these sites happened between June 2021 and November 2023.

Other areas have also been restored, such as the gun emplacement sites and the secret tunnels and plotting rooms located eight metres underground, which was no easy process.

The plotting room on its own was almost completely flooded, rendering the space inaccessible.

The Battery Plotting room.

“The first thing was to drain out the water, then remove all the cladding around the inside of the room, which had been soaked and rotten,” Peter explains.

“All the ceiling was exposed and steel beams were rusted. So that’s been stripped down completely, then repainted and preserved. Soundproofing was put in the walls, and then we made a table and simulated plotting arms, the radar table, and then repaired and rebuilt next door.”

The Australian Women’s Army Service played a crucial role during this time, working around the clock in the plotting room as men were sent off for active service.

Australian Women’s Army Service (AWAS) personnel, Plotting Room, North Fort at North Head, Manly. Photo credit: Eric Charles Johnston (Photographer), 1944

The room was manned 24/7 during the height of wartime. Its purpose was to receive the speed and directional coordinates from vessels spotted by the observation posts, plot their destination on a map, and, after some calculations, send the data to the gun emplacements.

North Fort featured a pair of 9.2-inch Mark X breech-loading guns, which were active until 1952.

Each gun is capable of firing a distance of 26.4 km, and with 360-degree spinning capabilities, the range could fire at vessels well out to sea, or even as far as Parramatta.

Rear view of 9.2 inch gun at North Fort Battery being fired during a practice shoot. Supplied: Harbour Trust

Although the guns have long been dismantled, Harbour Trust employees are undertaking work to repair and restore gun emplacement II.

Gun Emplacement I will be kept as a historic relic site but can be viewed by the public.

Unbeknownst to many during wartime, the guns were armed, powered and accessed by Army officials through 200-metre-long tunnels located eight metres under North Head Sanctuary.

Harbour Trust Defence of Sydney tour guide Ron Ray walks the tunnels of North Head. Image: Tikky Hes

“Beneath the guns, there is the ammunition room, and next door was the charge room that is kept separate, obviously for safety reasons. The projectile and the charge is brought on the elevation mechanism, and then it’s placed on a trolley which ran around the tracks of the gun,” Peter says.

“It was then brought up into the gun automatically. On the top level was the gun crew that operated the gun firing from data that was generated in the potting room.”

Astonishingly, the guns were powered hydraulically by large engines, also located underground.

Gunner loading a 9.2 inch shell on to a hand trolley at North Fort, North Head, Manly. Photo credit: Eric Charles Johnson (Photographer)

“Further down, at the beginning of the tunnel system, is an engine room which generated the electricity, which went into the pump room. The pump room provided the hydraulics to drive the gun,” Peter adds.

The newly restored North Fort observation posts at North Head Sanctuary are now accessible by the pathway extensions created by the Harbour Trust restoration volunteers.

Guided tours to visit inside the observation posts will be announced later this year.

The Harbour Trust offers the Defence of Sydney Tour at North Head Sanctuary on Sundays.

For more information, visit their website.

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