And so it is done; as I suspected without much fuss and I doubt whether it will cause The House of Windsor to implode. Just some 'tidying up' before it becomes an issue for William and Kate.R.I.
Well, I share your hope that this will passes nicely and without fuss; however, it is by no means done. Cameron and the other Commonwealth Realm prime ministers have merely agreed in principal to the changes. I was never much worried about that step. My main concern comes in the next phase - when each of those ministers actually starts to implement the plan back home.
Take Canada, for example. With patriation of the Canadian Constitution in 1982, a complete amending formula was adopted. Some parts of the Constitution may only be modified by a unanimous vote of all the provinces plus the two Houses of Parliament. These include changes to the composition of the Supreme Court of Canada, changing the process for amending the constitution itself, or any act affecting the Offices of the Canadian monarch or governor general. The succession would apply here.
So regardless of what Prime Minister Harper may have informed Prime Minister Cameron whilst in Perth, he has to get unanimous consent of all 10 Canadian provinces and both houses of Parliament. That will not happen without a great deal of debate in all the relevant chambers and bodies - debates which will no doubt call into question whether the time has come to end the monarchy in Canada all together. Quebec, in particular, has no strong affinity for the Crown and its refusal would effectively bring the debate to a halt.