I have no idea what this is, and am not sure if it is even an orchid. The only orchids I can think of that look even remotely close to this are Orthoceras and Speculantha. Very puzzling.
Thanks Matt; we haven't seen any since we were doing the border walk with the previous owners (2011) but this year the weather is a lot wetter and we might see some come January. I'll go for several walks and see if I can find any to get better pictures of them as they open.
There were no leaf type structures that I could see other than the beginnings of them that are part way along the flower stem.