In a recent letter to John Key, Australian Prime Minister Julia Gillard and the prime ministers of the fellow kingdoms of Antigua and Barbuda, the Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, Papua New Guinea, the Solomon Islands, St Christopher and Nevis, St Lucia, St Vincent and the Grenadines, and Tuvalu, Mr Cameron seeks support for bending the laws of succession. As one Canadian commentator says, it's like something out of Planet Goofy.
In the letter, Mr Cameron says it is "an anomaly" and goes against "gender equality" that women have to take their place behind younger royal males in the line of succession.
He writes: "In the UK, we have found it increasingly difficult to continue to justify two particular aspects of the present rules on the succession to the Crown. The first is the rule which says that an elder daughter should take a place in the line of succession behind a younger son. We espouse gender equality in all other aspects of life, and it is an anomaly that in the rules relating to the highest public office we continue to enshrine male superiority."
Mr Cameron also wants to remove the 300-year-old Act of Succession provision excluding potential heirs who "marry a Papist" from becoming monarch. He said this rule was a historical anomaly as it does not apply to those who marry spouses of other faiths. He draws the line at the monarch, happy to retain the anomaly she must not be a Catholic.
As the British monarch is also ours, Mr Cameron needs Commonwealth approval otherwise everything gets messy, constitutionally. That's why he's greasing up the other prime ministers, even though the tinkering he proposes will do nothing to improve the rights of any of their citizens, be they Catholic or Muslim, atheist or Buddhist, male or female.
The only people who stand to gain or lose by the proposed law change in 16 parliaments are the handful of blue bloods who can claim legitimate descent from the 17th-century Electress Sophia of Hanover, who was a granddaughter of James IV of Scotland (and James I of England) and the niece of Charles I.
Seems she was a Protestant, therefore acceptable, and ever since, her male heirs have had precedence over their sisters. All Mr Cameron's proposal will do is bring gender equality to this exclusive little aristocratic club. It certainly won't usher in a democratic selection process for our head of state, opening up the top job in any one of these 15 ex-colonies to a citizen of that land. Nor will it even enhance the human rights of the commoners of the United Kingdom.
Which takes us back to the set piece discussion on human rights and democracy which is the headline act at the Perth conference. Ms Gillard says the focus is on "the role of the Commonwealth in the age in which we live and how we can strengthen it for the future". In front of the 54 Commonwealth leaders will be the eminent persons' report on renewing the organisation, recommending a charter and the appointment of a commissioner for democracy, the rule of law and human rights. It notes "there is a growing perception that the Commonwealth has become indifferent because it fails to stand up for the values that it has declared as fundamental to its existence".
Fine words and dreams, for sure. But how seriously can you take an organisation that wants to set up a commissioner to fight for democracy and human rights in the same breath as it votes to perpetuate a feudal and undemocratic method of selecting its head citizen? Will John Key have the gumption to point this out?
