Tallest plants to around 40 cm, growing on a steep ant infested grass covered rocky scree slope. My hesitancy about the identification is that some of the yet to mature siliqua already exceed 40 mm and PlantNET descriptions give a range of 10-30 mm.
This plant was collected on 12 Dec 2018 and dried and pressed material was then taken to the CSIRO herbarium where Dave Albrecht determined it to be Cardamine lilacina based on the seeds being over 2 mm in length.