Commonwealth leaders are reported to be meeting to discuss the succession to Queen Elizabeth when she dies.
The Queen is thought to be backing her son, but success is not hereditary and will not pass automatically to Prince Charles.
So how will the decision be made? If it's a matter of which country's turn it would be, says royal watcher Richard Fitzwilliam, this could potentially be disastrous. "With a country like Sri Lanka, which has an extremely dodgy human rights record, that's the last possible solution that you want," he says.
Queen Elizabeth became head of the organisation in 1952. Over the intervening years, the world has gone through great change, which raises the question of whether the Commonwealth is still relevant.
But Fitzwilliam sees no reason why the Commonwealth should cease to exist.
"I don't think the Commonwealth will fall apart. If it was falling apart, you wouldn't have countries like Mozambique and Cameroon who have no connections with Britain who've joined it in recent years," he explains. "I don't think this will occur because there are special diplomatic ties with our High Commissioners rather than Ambassadors. The fact there are links with a very special form of soft power in the Commonwealth and that has prominence. So no, I think the Commonwealth will continue. The point is you want it to continue with the highest possible profile and that is linked to the world's highest profile royal family."
Perhaps it's too early to ask the question. At 91, the Queen is still in excellent health and her mother lived until she was 101.