Mr Justice Fancourt ruled the Duke of Sussex cannot bring his claim in relation to phone hacking, but the rest of his claim - relating to other allegations of unlawful information gathering such as the use of private investigators - could be tried.

He refused to allow the duke to amend his case to rely on a "secret agreement" between Buckingham Palace and senior News Group Newspapers (NGN) executives.

Harry alleges he was unlawfully targeted by journalists and private investigators working for NGN titles The Sun and the now-defunct News Of The World and is seeking damages.

At a previous hearing in April, NGN asked Mr Justice Fancourt to throw out the duke's case, arguing it was brought too late because he should have known sooner he had a potential claim.

In his written ruling, the judge concluded: "I am satisfied that there is no reasonable prospect of the duke proving at trial that he did not know and could not with reasonable diligence have discovered facts that would show that he had a worthwhile claim for voicemail interception in relation to each of the News of the World and The Sun.

"He already knew that in relation to the News Of The World, and he could easily have found out by making basic inquiries that he was likely to have a similar claim in relation to articles published by The Sun."

A spokesperson for NGN claimed the ruling was "a significant victory".

They added: "The Judge, Mr Justice Fancourt, found his claims in relation to the alleged 'secret agreement' were not plausible or credible.

"It is quite clear there was never any such agreement and it is only the Duke who has ever asserted there was."

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Hugh Grant's unlawful information gathering claims will also be tried

In May, Mr Justice Fancourt ruled a claim by actor Hugh Grant over alleged unlawful information gathering - other than allegations of phone hacking - can go ahead to be tried next January.

Grant, 62, is suing NGN in relation to The Sun only, having previously settled a claim with the publisher in 2012 relating to the News Of The World.

NGN has previously settled a number of claims since the phone-hacking scandal broke in relation to the News of the World, which closed in 2011, but has consistently denied unlawful information gathering took place at The Sun.

Harry, 38, has been involved in six legal battles at the High Court in recent months.

His civil litigation has seen him bring claims against three major newspaper publishers over allegations of unlawful information gathering, as well as legal challenges against the Home Office in relation to his personal security.