New Year's Day 1963. Two bodies are found on the banks of the Lane Cove River, about 18km north of the Sydney CBD.

The Bogle-Chandler case has never been solved. Over the decades, the theories kept coming, from Cold War espionage to LSD poisoning.

Then a 2006 documentary pointed to something far more mundane, a factory that had been quietly poisoning the river since the 1800s.

Watch the National Account’s Archie Milligan below: