"Elgin Marbles of Australian history"
Except we didn't go along and nick it to show off in a museum. It was drawn up by a British person working for the Royal Navy while a prisoner. So it's not really the "Elgin Marbles of Australian history" at all, as strictly speaking they have no right to "Demand" a bit of paper with their countries name written on it.
If they were nice about it then sure, give it to them. But if they are going to be dicks then I demand we not give this property over to the convicts.