What happens if a reigning sovereign marries a Catholic?

What would happen if a reigning British monarch were to marry a Roman Catholic? I know anyone in the line of succesion automatically loses their place but what happens when that person is already King/Queen? Are they automatically deposed? Didn’t George IV(aka the Prince-Regent) try to marry his Catholic mistress?

If I’m not mistaken, he DID marry her, but because of the Royal Marriages Act, which stipulated that the reigning sovereign had to approve all marriages of those in line for the throne, the marriage wasn’t considered valid.

As for them already being sovereign, I have no idea.

The 1701 Act of Settlement could not be more clear on the matter.

In other words, the monarch would immediately cease to be monarch and the Crown would automatically pass to their heir.

Actually, in the real world, that’s not what would happen. The moment a reigning monarch announced that they wished to marry a Catholic would be the moment the Act of Settlement was repealed.

As Guinastasia says, George IV did marry Maria Fitzherbert, but he was then prince of Wales and the marriage was invalid under the 1772 Royal Marriages Act. His mistress once he became king, Marchioness Conyngham, was Protestant. As her existing husband was happy for the three of them to form a ménage à trois, marriage was never an issue.

Not necessarily. I think (but I’m open to correction) that any amendment to the Act of Settlement requires the consent of the parliaments of all the commonwealth countries of which the British monarch is head of state. there are a very large number of these, and they generally have their own legislative and parliamentary priorities, so it could be extremely difficult to organise the necessary amendment, and consume a good deal of political and diplomatic capital. Moreover there is a risk that some at least of thes countries would be sufficiently annoyed or embarrassed by the whole business at least to consider breaking the link with the crown.

My guess is that considerable pressure would be brought to bear on the monarch to change his or her choice of marriage partner, or on the partner to adopt some other religion, or none at all.

It is often said that Wales’s current squeeze, Mrs Parker-Bowles is a Catholic, though according to the BBC she’s not; she was married to a Catholic, but was never received herself. But the dilemma could arise at any time.

But it is now utterly inconceivable that any government in the UK would wish to be seen to object to such a marriage on the grounds that the proposed spouse was a Catholic. Viewed entirely cynically, there would be much political capital to be gained by politicians supporting the marriage and much to be lost by opposing it (even after factoring in the Ulster Unionist complication). And the same would be true for most Commonwealth governments as well.

Doesn’t the Royal Marriages Act state that the monarch CAN’T marry a Catholic, and therefore no matter what ceremonies he may go through the marriage is invalid?

So the simple answer is - he can’t.

For the marriage to be recognised he would have to abdicate in favour of his heir.

That’s what the law reads today. I was understanding APB to be saying that if an Edward VIII-type situation occurred today (i.e., in the immediate future), the law would most likely be changed to accommodate the monarch’s wishes, rather than forcing another abdication.

I don’t know what became of Fitzherbert, or whether or not the marriage was officially dissolved. But before he became King, the Prince Regent married again, to Princess Caroline of Brunswick. (Although she was never crowned-the woman was a slob-never bathed, ugly, horrible flatulence, etc).