The 53-year-old had the surgery at Oslo National Hospital. This was confirmed in a statement on Wednesday. The statement read: "Her Royal Highness Crown Princess Mette-Marit has undergone a successful lung transplant at Oslo University Hospital Rikshospitalet in Oslo."

The statement also confirmed that the lung transplant has been successful so far in the view of Arnt Fiane, Professor of Medicine at University of Oslo, cardiothoracic surgeon and Head of the Heart and Lung Transplant Programme at Oslo University Hospital Rikshospitalet.

This is because the hospital team caring for the princess need to adjust medication and manage any potential complications.

During this time, her husband His Royal Highness Crown Prince Haakon may change some of his scheduled engagements so he can be there to support his wife.

No further updates are expected under the royal is discharged from hospital.

The Palace said: "The Crown Prince and the Crown Princess express their sincere gratitude for the many warm and kind messages they have received. This means a great deal to them at this challenging time."

The news of her surgery comes as her son Marius Borg Høiby has been found guilty on two counts of rape and was sentenced to four years in prison. The 29-year-old was on trial for a total of 40 charges, including allegations of raping four women as well as domestic abuse and other crimes.

He pleaded not guilty to the four charges of rape. However, he pleaded guilty to several driving offences, to an aggravated drugs offence and breaking a restraining order, and “partly” to threats and aggravated assault. According to the BBC, the Oslo District Court cleared him of two other counts of rape, but found him guilty of many of the other offences of which he had been accused. He was not in court for the verdict, but joined the session via video link.