As Cyclone Tracy's ferocious winds lashed Darwin, St John Ambulance volunteers answered the calls for help, setting the stage for 50 years of service to the Northern Territory.

Cyclone Tracy, which started as a weak tropical low in waters north of Darwin, slammed the city as a category four system, killing 71 people and forcing the evacuation of thousands of others.

On Christmas Eve 1974, Tracy flattened Darwin, killing 66 people. The city is still at risk of cyclones, and not enough has been done to mitigate it.