There hasn't been any discussion of investiture here as for Governors General, the honour is bestowed automatically. The Governor General is ex-offico the Chancellor & Principal Knight/Dame of the Order Of Australia by virtue of holding the office.
For Dame Quentin Bryce, this occurred the moment the Queen, on advice of the Prime Minister, signed the letters patent authorising the reintroduction of Knighthoods / Dameships.
General Sir Peter Cosgrove was elevated to that rank when he was sworn in by the Chief Justice of the High Court on the floor of the Senate of Australia.
As for how future recipients (who aren't also becoming Governor General) will receive the honour the Prime Minister states;
"Well, this is really a question for the recipient of the award. Let's not forget that the Queen is actually the Sovereign of the Order of Australia and my understanding is that it is not entirely unknown for people who receive an award in the Order of Australia, as things stand, to receive their honour from Her Majesty. On the other hand, it is also quite common for people who receive these awards in the Order of Australia to receive the honour from their [State] Governor or the Governor-General."
There is no way Prince William will be involved in any investiture whilst he is visiting. The Prime Minister (an avid monarchist) has already been criticised widely by republicans and the media for what is seen as an anachronistic move.
The very last thing he or the monarchist movement need is the image of a Junior Royal (Albeit well liked and respected here) holding the position of authority over the Governor General (Who is widely regarded as the de-facto head of state) in an investiture ceremony.
You could also rule out The Duke of Cambridge receiving an Australian Knighthood on this trip. The Prime Minister has had to reaffirm that this is not a return to Imperial awards but an Australian award for Eminent Australians who have given extraordinary service to the nation. It has been capped at 4 new members per annum. To award one to William so soon after announcing it with these terms would be political suicide and do great damage to the monarchist movement.
If Australia remains a constitutional monarchy he may receive one when he is heir to throne, as his father has, but I very much doubt before then.
My best guess for the next appointment would be former Governor General, Major General Michael Jeffries. The other former Governors General who don't yet have a Knighthood most likely won't receive the honour as Bill Hayden, a former Labour politician, holds a Companion of the Order of Australia only by virtue of being the Principal Companion as Governor General and has previously declined all other honours and Peter Hollingworth resigned his office in controversy.
Originally Posted by Sun Lion
- but it has been revealed former Prime Minister, Ms Julia Gillard, is the one who wrote to Her Majesty The Queen - who agreed and issued the Letters Patent - which enables Dame Quentin Bryce to be known as "The Honourable" - for life.
I must say It annoys me that they are granted "The Honourable" whilst still holding office as the are already styled "Your Excellency". It makes it very Clunky, we now have 'His Excellency The Honourable General Sir Peter Cosgrove'.
It would have made more sense for the sitting GG to be styled 'His/Her Excellency' and upon retirement 'The Honourable' (or even 'The Right Honourable' but thats another argument).
Anyway thought I'd sign up to offer some clarity on the issue, hope it helped.