Ann: Trading Halt, page-48

Preparatory work will take at least that long. Clearing, pad preparation, setting up camp and offices, access roads etc. It's a long list.
I worked on the Roy Hill Iron Ore Project and building the infrastructure took just over 2 years, mining didn't 'officialy ' begin until after that.

My prediction is that TNG will release a detailed schedule of works showing the timing and expected duration of works planned over the next 12-18 months. They will show how they will meet these approval conditions whilst also preparing the site so as to not lose any time.
Don't forget the announcement not long ago bringing on the EPC (can't remember who). They are there to assist during this phase. TNG have been waiting for this. I think it is all systems go.