Norway's Marius Borg Hoiby was found guilty of two counts of rape against a former girlfriend. (AP PHOTO)Norway's Marius Borg Hoiby was found guilty of two counts of rape against a former girlfriend. (AP PHOTO) Credit: AAPMarius Borg Hoiby, the eldest son of Norwegian Crown Princess Mette-Marit, must remain in pre-trial detention for a further four weeks, an Oslo court has ruled. The 29-year-old will continue to serve the detention under house arrest with an ankle tag, the news agency NTB reported. Police argued there was a risk of Hoiby committing further offences and requested an extension of the house arrest.