Looks young to me too (within 3 years old I guess) but I have yet to come to grips with ageing them, even crudely. (Actually our conservation advice could be better if demographic rates were known for some populations of this species, but that is not possible until there is an accepted ageing method for wild individuals.)
Many thanks Gillian for posting this. There is only one other local goanna species, nearly gone now from the ACT region, and your photo is plenty good enough to see it was not that one.