King Charles expresses 'deepest concern' after brother Andrew Mountbatten-Windsor's arrest

King Charles III expressed his "deepest concern" about the news of his brother, former Prince Andrew, being arrested on suspicion of misconduct while in public office.

"What now follows is the full, fair and proper process by which this issue is investigated in the appropriate manner and by the appropriate authorities. In this, as I have said before, they have our full and wholehearted support and co-operation," the king said in a statement.

"Let me state clearly: the law must take its course," he added. "As this process continues, it would not be right for me to comment further on this matter. Meanwhile, my family and I will continue in our duty and service to you all."

On Thursday, Thames Valley Police issued a statement on a newly opened misconduct probe. Without naming the person at the center of the case, police said that "a man in his sixties from Norfolk" was arrested on suspicion of misconduct while in office. Thames Valley Police said that officers were carrying out searches at addresses in Norfolk and Berkshire. 

"Following a thorough assessment, we have now opened an investigation into this allegation of misconduct in public office," Assistant Chief Constable Oliver Wright said in a statement. "It is important that we protect the integrity and objectivity of our investigation as we work with our partners to investigate this alleged offense."

"We understand the significant public interest in this case, and we will provide updates at the appropriate time," Wright added.

Thames Valley Police said the man would not be named, citing "national guidance."

Mountbatten-Windsor, who turned 66 on the day of his arrest, was previously linked to disgraced late financier Jeffrey Epstein, and has appeared in the infamous Epstein files, including in images.

Police had previously said that they were looking into reports that Mountbatten-Windsor had shared confidential trade reports with Epstein in 2010, when the then-prince was serving as Britain’s special envoy for international trade.

If the case were to go to trial, it would head to the UK's Crown Court, which deals with the most serious criminal offenses, and the former prince would be facing life behind bars. Additionally, U.K. law limits the amount of time that Mountbatten-Windsor can be held in detention to 96 hours. 

The Crown Prosecution Service, the main prosecuting agency in the U.K., says misconduct in public office is committed when a public officer willfully neglects their responsibilities and/or willfully misconducts themselves to such a degree as to amount to an abuse of the public's trust. Furthermore, the offense must be done when the person is acting as a public officer, meaning it would not be relevant if the individual had committed a crime while holding office.

This is a developing story. Please check back for updates.

The Associated Press contributed to this report.