Whether it’s from the presence of the Liberal Democrats or from David Cameron’s own convictions, Britain’s coalition government is steadily building up some reformist credentials. Latest cab off the rank is a plan to revise the archaic rules of succession to the British monarchy, which just so happens to be our monarchy as well.

The proposed changes are twofold: to introduce parity between the s-xes in succession, rather than have males of the same degree outrank females (so elder daughters would succeed in preference to younger sons), and to remove the disqualification that currently affects any prospective heir who marries a Roman Catholic. It is also planned to limit the scope of the Royal Marriages Act of 1772.

Most of the media coverage has described this as a change to the Act of Settlement of 1701, but that’s only half right. The act does indeed codify the restrictions on Catholics; section 2 disqualifies “all and every Person and Persons who … is are or shall be reconciled to or shall hold Communion with the See or Church of Rome or shall profess the Popish Religion or shall marry a Papist”.

As to who gets to be in line for the throne in the first place, however, all it does is confer the succession on “the said most Excellent Princess Sophia and the Heirs of Her Body being Protestants”. It was (and is) a simple matter of common law, not requiring any statutory comment, that the expression “heirs” gave priority to males over females.

The Act of Settlement was passed following the death of the only surviving child of Princess (later Queen) Anne; together with the childlessness of the recently widowed King William III, that created a gap in the succession. The next 50 or so best claimants by blood (including Anne’s father, the deposed James II, and his son, the Old Pretender) were all Catholics, and the revolution of 1688 had made it clear that England’s governing classes would not wear a Catholic monarch.

So Sophia, dowager electress of Hanover and grand-daughter of James I, was the choice; she failed by a few weeks to outlive Anne, but her son duly became king as George I, and the current queen, nine generations later, is his direct descendant.

A lot has changed in 300 years, but the essentials of the revolution settlement are still in place. The monarch is still head of the Church of England, its bishops still sit in the House of Lords and it remains an integral part of the state in a way that would be regarded as unacceptable in most other democracies. Even if it wanted to, for a British government to disentangle that relationship would be a mammoth task.

But until it happens, the idea of a monarch who is beholden to a rival religion is deeply problematic. Since 1910, heirs are no longer required to explicitly repudiate the various key doctrines of the Catholic Church, but they must still still declare “that I am a faithful Protestant” and promise to uphold “the true intent of the enactments which secure the Protestant succession to the Throne of my Realm”.

In other words, the proposed changes are limited in scope, and the only likely objection to them is that they do not go far enough. For Australia it raises the question of whether, if we remain unwilling to bite the bullet and vote for a republic, we could at least remove the religious restrictions on the monarchy for ourselves — given that we have no established church to complicate matters.

Official opinion downplays this possibility; Cameron proposes to secure the consent of the other 15 countries (including Australia) that recognise the Queen as head of state. Nobody seems to want to think about different countries adopting different succession rules.

It is nonetheless perfectly possible — that’s how Britain and Hanover separated in 1837. While section 2 of the Commonwealth of Australia Constitution Act limits our crown to “Her Majesty’s heirs and successors in the sovereignty of the United Kingdom”, that is not part of the constitution. It’s an ordinary act of parliament, and could be amended by the Australian Parliament if it chose.

But that view remains controversial, and since the Gillard government clearly has bigger things on its plate, expect it to again let the British take the lead and do no more than fall in behind the Cameron plan.