Andrew Mountbatten-Windsor is taking Thames Valley Police to court over his February arrest on suspicion of misconduct in public office, challenging whether the search warrants for his homes were lawful.

He was detained on his 66th birthday, February 19, and questioned for around 11 hours at a police station in Norfolk after emails released in the Jeffrey Epstein files suggested he had shared sensitive information with Epstein while serving as Britain's trade envoy between 2001 and 2011. Detectives held him while officers searched his residence on the Sandringham Estate and his former home at Royal Lodge in Windsor, acting on warrants issued by a judge.

According to the Telegraph, which first reported the legal challenge, Mountbatten-Windsor has lodged a judicial review asking a judge to determine whether the force acted lawfully. A private hearing is set for October 8 at the High Court before Mr Justice Hilliard, where Thames Valley Police will seek to restrict access to court documents. The force said its investigation into misconduct in public office continues and that it would be inappropriate to comment further while legal proceedings are ongoing. He was released under investigation and has not been formally charged.

The case is historic in its own right. It is the first time a member of the royal family has challenged the lawfulness of criminal actions against them since the trial of King Charles I in 1649, a comparison that has underlined the constitutional sensitivity of the proceedings and the extraordinary position in which the former prince now finds himself.

Mountbatten-Windsor, the younger brother of King Charles, was forced to quit all official royal duties in 2019 over his ties to Epstein and was stripped of his titles and honours last October amid further revelations about the relationship. He has denied any wrongdoing and said he regrets the friendship. The Epstein files, released by the US Department of Justice in late January, have triggered investigations on both sides of the Atlantic, and the allegations centre on whether confidential government material was passed to the late financier.

For the former prince, the judicial review is a high-stakes attempt to have the warrants quashed and to undermine the investigation at its foundation. For the police, the outcome will shape how the continuing inquiry proceeds. Whatever the court decides, the case has already become one of the most extraordinary legal confrontations in modern royal history, pitting a king's brother against the force investigating him.