Fortunately I somehow lived until I got to Darwin. Oh, it was great to be in Australia. Not only could I put in a full position flight plan, but because I was going over 50 miles (heading from Darwin to Sydney) it was compulsory.
Dick, I think it was only compulsory for charter. Private flights have always been able to go nosar. Sure it was frowned upon, called "nosar, no sense" and all that garbage but it was a legitimate and legal way to fly. I did it way back then (to the disgust of Flight Services), you could have too.
I think you were bluffed and you could have legally flown Darwin to Sydney with no plan.