Calochilus. Could be either platychilus or therophilus. Way taller than either of them usually are (500mm). Much later than the other platychilus that have been and gone. Also much earlier than the therophilus usually are (still to appear). Anomalies could always just be a function of the season.
We see them most years. But not until the end of January usually. And this one is exceptionally tall ... over 600 mm now. And the flowers are not yet all out. So odd.
A feature of C. therophilus is a progressive flower opening over several weeks. With the lower flowers opening first and each successive flower/s opening then closing up the stem rather than a more complete group opening.
It is odd that it is so tall not that the flowers are not yet all out. It will be taller when the flowers are finished. And yes they do open successively. Most of them are down at the 300 mm height rather than double that and probably taller by the time it has finished flowering.
Yes, 600mm is tall but the suggested height is 400 - 950mm and I know I have seen them that tall on Black Mountain in the ACT. The other thing about this genus to consider, besides seasonal changes/responses to growth, is its observed development over years, where individual plants increase in size each year as they develop and appear to, following some trigger, to put all their effort into a greater flowering followed by them then apparently exhausting. While this an explanation for the observed behavior I am not sure if this has been specifically studied or yet confirmed.
Well this is a new plant. A reasonable distance from the other therophilus here. And in a place that it would be very hard to miss when flowering. So I guess we can expect it to be even taller next year. Frightening thought.