A longhorn beetle, it looks like a Tropis species: http://www.ento.csiro.au/biology/cerambycidae/info_pages/Tropis.html And https://bie.ala.org.au/species/urn%3Alsid%3Abiodiversity.org.au%3Aafd.taxon%3Ac282c305-2def-4bec-a92e-e4c0d31e467e#gallery
Thanks Michael. That looks like it, doesn't seem to be much info on it though. It was on a tree branch about 1.5m off the ground, but flew as I tried to photograph it.
I think this looks more like Tropis exilis; the shape of the elytra and prothorax match the figure of that species given on the CSIRO website cited above by Michael. The tufts on the antennae are probably not a reliable feature to use, as they will likely wear off over time.