When the couple marry, the palace said Durek will not have a royal title or represent the monarchy.

The pair have also agreed not refer to Martha Louise's title or the royal family in social media or commercial activity.

The statement added: " “This is intended to draw a dividing line that more clearly separates commercial activity from the royal house of Norway.”

Martha Louise - who claims to be able to "speak with angels" - stressed her gratitude for Norway's "high-quality health-care system" and said she is "aware of the importance of research-based knowledge".

She added in a statement: ““I also believe, however, that there are components of a good life and sound physical and mental health that may not be so easy to sum up in a research report.

"A warm hand, an acupuncture needle, a crystal, natural remedies, yoga, meditation or therapeutic conversation can, I believe, help to make life better for many individuals."

The princess, who has three daughters with late ex-husband Ari Behn, thinks it is important to "distinguish between myself as a private person on the one hand and as a member of the royal family on the other”, and expressed her hope that her personal views would be treated as her own “without others having to answer for them”.

Martha Louise lost her 'Her Royal Highness' title in 2002 when she began working as a clairvoyant.