Marius Borg Hoiby, the son of Norway’s Crown Princess Mette-Marit, has been arrested in Oslo on suspicion of rape. The 27-year-old man, who was detained late on Monday, is facing a serious charge: he is accused of having sexual intercourse with someone who was unconscious or unable to resist.

Marius is not a royal titleholder, as he was born from Mette-Marit's previous relationship before she married Crown Prince Haakon, the heir to the Norwegian throne. Although he does not have officia...