Northland mystery revealed: What is behind The Frenchman’s puzzling doorway?

Lionel Sands has opened the door on Frenchman Island's mystery. Photo / Tania Whyte

A concrete door hidden away on a small rocky island at the entrance to the Whangārei Harbour has created quite a stir of theories as to its existence.

An article by Stuff highlighted Frenchman Island’s strange doorway sealed with concrete and framed by rounded pillars with three steps at its feet.

Rumours about the door claimed it was used to conceal explosives or was a wartime decoy. Some people suggested the door was linked to past smuggling in Whangārei Heads where in the 19th century cargo, like tobacco and whisky, was stowed away at nearby Smugglers Bay.

The mystery door on Frenchman Island. Photo / Tania Whyte

But Whangārei Heads local Lionel Sands was handed the key to the door’s mystery 70 years ago, as a 6-year-old, by his father.

“I learned it wasn’t a door to a secret cabin,” he said. “There are no pirates, no villains, or anything like that - it’s actually very boring.”

Sands’ father shared the secret with his son when he spoke of Sands’ grandfather, Marmaduke Lionel Sands.

“He worked for the Whangārei Harbour Board in the 1920s servicing the light on the Frenchman [Island],” Sands said.

Marmaduke was also charged with maintaining the light on Coppermine Island (Mauipane) near the Hen and Chicken Islands.

And as he did so, Sands’ father would tag along.

That is how he learned the door - once wooden until it became too weathered - veiled a concrete recess used to store cylinders that fuelled the light at the island’s peak.

Marmaduke Lionel Sands used to service the light on top of Frenchman Island. Photo / Supplied

An Advocate article from 1913 wrote of the Whangārei Harbour Board officially lighting the acetylene light on Frenchman Island in January of that year.

“When my grandfather was servicing the light, my father said he could fill the boat up with blue cod from the waters around the Frenchman,” Sands said.

He explained how on Coppermine Island, the cylinders were kept in a little shed.

“There’s not a lot of mystique to the door,” Sands said. “But it’s good to have the stories.”

He thought his father and grandfather would have had a good chuckle hearing the theories.

“It’s pretty neat for young people to have the mystery of the door on the Frenchman - it’s like a fairytale.”