I know. That's why I put "hybrid" in brackets afterwards. Most likely it is the plant you can buy in nurseries as Microcitrus papuana. I think the consensus on the forum was that it's a hybrid. It is quite difficult to name this hybrid (which is sold as true papuana/wintersii) in a way that everybody understands what is meant.
There are lots of citrus plants incorrectly named as Citrus wintersii/Microcitrus papuana. I could add the one at Palais Carnoles to the others I have described at www.homecitrusgrowers.co.uk/australianpngnativecitrus/citruswintersii.html The thin-leaved Italian specimens are closest to the original description, but the tiny flowers are very strange and the fruits not quite correct either.
There was a fruit on the ground. It resembled the "fatter fruits" of the hybrid types but not at all the fruits of the true wintersii. Sadly I`ve taken no picture. citrange feel free to use the pictures as you like.