Although it had long been expected, Queen Beatrix of the Netherlands today announced that she intends to abdicate in favour of her son, who will become King William Alexander, on 30 April. Her Majesty announced so herself in a prerecorded television broadcast. And with the new king, we will also get a new queen, and she is Catholic.
Princess Máxima hails from Catholic Argentina and still seems to be practising her faith. Although she will not be head of state, she will be the first Catholic monarch in the Netherlands, member of a royal house which rose to prominence in the fight against Spanish Catholic rulers.
In reality this will not mean a whole lot. As consort of the king, Queen Máxima has no political power, nor will there be any measures that need to be taken to satisfy constitutional demands. Those that did exist were tackled when the royal couple married in 2002.
The one question that remains is whether there will be a Catholic contribution to the investiture. Although Protestant, the royal family has for years had close personal contacts with former Catholic priest Huub Oosterhuis, who still sometimes pretends to be Catholic. But what religious form the investiture will take remains to be seen. We can, however, be sure that there will be protests at the mentioning of God in the oath that the king (“by the grace of God”) will be taking…
Photo credit: Erwin Olaf
In Caelo et in Terra 
The thing closest to religion will be the oath or perhaps a recessional hymn (cf. investiture of Beatrix). The ceremony is in fact a joint session of both chambers of parliament, regulated by a law passed in 1992, which I think precludes an active role for Mr. Oosterhuis.