I thought I'd read that there was a provision in the Corporations Act that once you go over 20% you have to mount a takeover?
No, once you are over 20% you can only increase your shareholding by 3% each months without launching a formal takeover. This is the same method that SQ,NZ and EY are currently increasing their holdings in VAH without a takeover though at some point they will do this so they can delist and achieve the savings that will flow from that.