For 30 years, crooked cops extorted and intimidated these sex workers. Until the women fought back

Dorothy Edith Knight at New Farm Park, where in 1971 she put herself in grave danger. (ABC RN: Tammy Law)

The elderly woman, if you noticed her at all, could be your grandmother, inching slowly along the shaded path with the help of a black walking stick.

We're waiting for her at a bench in New Farm Park in Brisbane's inner-north. Young professionals in lycra powerwalk the riverside track. Purple electric scooters whiz by kicking up fallen jacaranda leaves in their wake.