As one Catholic commentator put it last week, “it had to happen sooner or later, and now it has.”

The “it” was a call by an Islamic leader in Italy for polygamy to be legalised. Now that Italian law recognised same-sex civil partnerships, argued Hamza Piccardo, leader of the Union of Islamic Communities, there was “no reason” for polygamy to be forbidden.

This sort of argument was precisely what critics of gay marriage laws predicted; redefine marriage to incorporate the union of two men or two women and soon there will be calls for other types of union to fall within this definition as well.