Are you sure about this donhe? I'm not sure i can see a projecting single spine at the rear of the caterpillar. And it looks quite different to those for this species on LBH.
The colours of C. kingii larvae are variable, the tail spike is blurred (visible beyond an intervening twig), and that is a Gardenia, and the posture is typical of Cephonodes.
OK, I can see C. kingi and other Cephanodes larvae are variable. But can you rule out other Cephanodes species, see here: https://www.inaturalist.org/taxa/121833-Cephonodes-hylas Also the ALA shows C. hylas comes to sother=thern laitudes too, see here: https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:45277dcb-4595-4a6d-928e-2410fa4df72d#gallery
I admit I have only found (and reared) C. kingii in Sydney, and know little about the other 3 much rarer Cephonodes species larvae, except from Max Mould's book. So I think statistically it is most likely C. kingii. Of course the only certain method of determination would be to rear it in captivity to get the adult moth. Can you do that Rebecca?