Thanks Tyrlych.....Melanthera is interesting. Not one I know. Melanthera biflora even appears as a listed plant for Norfolk Island. List of vascular plants of Norfolk Island - Wikipedia However I haven't yet managed to find a good match for the leaves.
It kind of reminds me of the plant in this thread: Yellow-flowered shrub, California native? I had never heard of Verbesina before -- 200 or more species. DYA.
Thanks for your help Eric...you too are correct! To clear up this mystery I e mailed Norfolk Island Flora and Fauna group. Their verdict is........."Wollastonia biflora (Mile-a-minute) First named Verbesina biflora, then Wedelia biflora and Melanthera biflora" I still feel the leaves on my pics differ but have to accept local knowledge/expertise. Wollastonia biflora - Google Search .