Image source, Getty ImagesImage caption, Princess Amalia – seen with her father the king – turns 18 in December and is expected to go to university

Same-sex marriage has been legal in the Netherlands since 2001 but it has always been assumed that it could not apply to the crown as there would have to be an heir to the throne.

Now caretaker Prime Minister Mark Rutte has made clear any king or queen could also marry a person of the same sex.

The heir to the Dutch throne, Princess Amalia, turns 18 in December.

Mr Rutte said it was all about "theoretical situations" but the next queen could marry a woman.

"Therefore the cabinet does not see that an heir to the throne or the king should abdicate if he or she would like to marry a partner of the same sex," he explained in a response to a written question in parliament from his own party.

As King Willem-Alexander's eldest child, Princess Amalia's future has come under scrutiny, with one book over the summer raising the issue of what might happen if she chose to marry a same-sex partner.

The book did not speculate over the princess's personal life, and there is no indication of any wedding in the pipeline. Amalia is expected to go to university next year and she has declined the royal income she is entitled to while she is a student.

The question prompted two MPs from Mr Rutte's own liberal VVD party to ask whether current restrictions on royal marriage met with the "norms and values of 2021".

Although the cabinet makes it clear that same-sex marriage is possible, what is not known is what would happen to the succession if there were children born from a same-sex royal marriage, for example via adoption or a sperm donor.

"It's frightfully complicated," Mr Rutte explained. The Dutch constitution states that the king or queen can only be succeeded by a "lawful descendant".

The prime minister said that it was purely theoretical at this stage but it would be up to parliament, which has to give approval to a royal marriage. "Let's cross that bridge if we come to it," he told Dutch TV.

You may also find this of interest:Media caption, Prince William said in 2019 that he would "fully support" his children if they were gay