Prince Harry prepared to risk relationships with King Charles and Prince William in pursuit of his mission - analysis by Cameron Walker
Prince Harry returned to the UK in a surprise appearance at the High Court
PA
The Duke of Sussex sees it as his mission to hold powerful people to account who were allegedly involved in unlawful or unethical information-gathering at British tabloids.
Ever since his mother Princess Diana was killed in a car crash in Paris, the Prince has blamed the press for what he sees as their part in her death.
It is a theme he has repeatedly referred to in his recent memoir, and numerous TV interviews, over the last few years.
The Duke alleges illegal practices (such as phone hacking) contributed to undesirable stories about him appearing in British tabloids.
Prince Harry stepped down as a working member of the Royal Family in 2020
PA
But the rift runs deeper than the occasional embarrassing headline.
Prince Harry has a problem with what he sees as unethical culture and practices at British tabloids, and how they source their information.
He and Meghan stepped back as working members of the Royal Family, partly to free themselves from "playing the game" in the royal rota system, and their desire to go on the record to defend themselves from stories they claim are untrue.
This is perhaps why he has joined forces with other well-known figures to bring legal action against Daily Mail publisher Associated Newspapers over allegations of unlawful information-gathering.
Associated Newspapers Limited has previously described the claims as "preposterous smears" and "unsubstantiated and highly defamatory claims".
The Duke of Sussex is even prepared to risk his own relationship with his father and brother over his pursuit of the British press.
He alleges Royal Family members' staff briefed against the Sussexes to improve their own principals' image; an allegation Buckingham Palace has not commented on.
The Prince has also talked of his fear of "history repeating itself", perhaps referring to his fear that Meghan could suffer a similar fate to Princess Diana.
Prince Harry and Prince William are not expected to meet face to face during the Duke of Sussex's trip to the UK
PA
The war against the press is seen by Harry as his "life's work" - bringing justice to other victims of alleged tabloid practices.
He doesn't appear to be in this fight for financial damages and an out-of-court settlement is unlikely.
Today Prince Harry is, quite literally, having his day in court and this can be taken as an indication of how determined he is to hold powerful people to account and change the way the British media operates.