A number of the Heliothinae caterpillars look like this, see http://lepidoptera.butterflyhouse.com.au/heli/heli-cats.html On what plant was it feeding? Are you rearing it to get the adult moth?
It was feeding on a Great Mullein (Verbascum thapsus), the plant is shown in one of the images. Given this is an exotic weed I was thinking it may have been one of those situations where this caterpillar/moth could have been introduced for biological control (But honestly I have no idea). Unfortunately I didn’t collect it to rear it.