The Duke of Sussex is due to discover whether his legal challenge over allegations of unlawful information gathering against a tabloid publisher can continue to a High Court trial.

Harry, 38, alleges he was targeted by journalists and private investigators working for News Group Newspapers (NGN) titles The Sun and the now-defunct News Of The World and has launched a claim for damages.

At a 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.

The judge is expected to deliver his decision on whether the duke’s claims can go to trial at 10am on Thursday.

The ruling is also due to cover whether the duke can rely on an alleged “secret agreement” between the royal family and senior executives working for media mogul Rupert Murdoch as part of his claim.

Harry’s lawyers previously argued that NGN’s challenge to his claim is an attempt to go behind the alleged “secret agreement”, between the royal family as an institution and the publisher, which the duke was told of in 2012.

But NGN, which denies any unlawful activity took place at The Sun, disputes such an agreement was in place.

At a hearing in London earlier this month, lawyers for the duke said there is evidence to support the existence of the agreement, including emails between senior executives at the Rupert Murdoch-owned parent companies of NGN and palace staff in 2017 and 2018.

David Sherborne, for Harry, also said in written arguments the fact the Prince of Wales settled a claim against NGN “for a very large sum of money” in 2020 also “supports the contention that there was a secret agreement in place”.

But Anthony Hudson KC, for NGN, told the court the bid to alter the duke’s claim is a “radical intended revision” of his case and he is “trying to ride two horses galloping in completely different directions” and “hedge his bets”.

Mr Hudson said the alleged agreement was “such a secret agreement that no-one apart from the claimant knows anything about it, and even the claimant knows very little about it”.

The barrister also said there was an “extraordinary delay” between Harry launching his claim against NGN in 2019 and first raising the issue of the “secret agreement” following the publisher’s strike-out bid.

Mr Justice Fancourt ruled in May that 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 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.