The son of Norway's Crown Princess Mette-Marit has been arrested by police on suspicion of assault, before he goes on trial in Oslo on Tuesday on 38 charges, including the rape of four women.

Marius Borg Høiby, 29, was remanded in custody for four weeks. Police said the latest allegations against him involved wielding a knife and violating a restraining order, and there was a risk of reoffending.

His arrest on Sunday is the fourth time he has been detained by police since August 2024, when he was accused of assaulting a woman he had been having a relationship with.

He has denied the most serious charges against him but admitted some of the more minor ones.

It is the latest scandal to beset the royal family.

Norwegians are also coming to terms with revelations that his mother corresponded for three years with late sex offender Jeffrey Epstein between 2011 and 2014.

Crown Princess Mette-Marit admitted "poor judgment" as her extensive contacts with Epstein became clear. She expressed her "deep sympathy and solidarity with the victims of the abuses committed by Jeffrey Epstein" and said her contact with him was "simply embarrassing".

It has emerged that she stayed at his Florida home for four nights, while he was not there, and asked Epstein if it was "inappropriate" for a mother to suggest to a 15-year-old son wallpaper showing two naked women carrying a surfboard.

Prime Minister Jonas Gahr Støre said he agreed with her admission of "poor judgment", and although he did not go further, his implicit criticism of her actions is highly unusual.

Questions are now being asked in Norway about her failure to realise the toxic nature of maintaining contact with Epstein, and about the role of her advisers when she was corresponding with him via an official royal email account.

"It seems that nobody has been thinking. Where are the counsellors, where's the royal court and where's the foreign office?" says Ole-Jørgen Schulsrud-Hansen, a historian and royal correspondent for Norway's TV2.

He believes the monarch has managed to distance itself from the imminent court case, with the argument that the princess's son is a private citizen, but that is not the case for Mette-Marit: "She's never a private citizen, she's always the crown princess and what she's doing in a private capacity or official capacity it will always redirect back to Norway - or ricochet."

Mette-Marit is the future queen of Norway, and she has a prominent role in society as patron of several organisations including the Red Cross.

She is also suffering from pulmonary fibrosis and her doctors are preparing to put her on a list for a lung transplant.

When Mette-Marit married into the family as a commoner, her son was already four years old.

Although Marius Borg Høiby is not a member of the royal family, he is still Crown Prince Haakon's stepson.

The charges against him range from rape and abuse to violating a restraining order, transporting 3.5kg of marijuana and speeding.

When he was first arrested in 2024, he spoke of having several mental disorders and struggling with substance abuse. Since then, he has spent only a week in custody, so the police's request to remand him for much of the trial is a change of stance on their part.

The Oslo District Court said in a statement quoted by Reuters that it had agreed to the police request to prevent repeated offences.

The royal household has sought to distance itself from the trial, and in a statement last week, Crown Prince Haakon reached out to the women caught up in the case and their families, saying it was "a difficult time for many of you, and we sympathise".