The trial is expected to last between six and eight weeks with a further hearing due to be held in December.
The Duke of Sussex “is one of two claimants whose claims are still live” against the publisher of The Sun over allegations of unlawful information gathering.
A hearing on Friday was told that Harry and former Labour deputy leader Tom Watson are now the only people continuing their claims against News Group Newspapers (NGN).
The court was told 39 cases have been settled since a previous hearing in July.
The two remaining cases are expected to go to trial in January 2025, with Harry alleging he was targeted by journalists and private investigators working for NGN, which also published the now-defunct News Of The World.
The publisher has previously denied unlawful activity took place at The Sun.
Speaking on Friday, David Sherborne, for the claimants, said: “The reduction of the live claims to just two is a pretty recent development.”
The two sides returned to court in London to ask a judge to rule on preliminary issues before the trial in the two remaining cases, with Lord Watson in attendance at the hearing.
The judge ruled Harry can use further emails between executives of the publisher of The Sun and members of the royal household in his legal claim.
The messages were sent between a number of former NGN executives and members of the royal household between 2013 and 2019.
Mr Justice Fancourt said there was a “degree of speculation whether any of the documents sought are going to assist the claimant’s case”, but ruled there was “sufficient justification” for some of the emails to be provided.
He said: “In all the circumstances, therefore, it seems to me that there is a limited category of documents where despite the element of delay, and despite the relative lateness of the application, there is a credible case for saying a full picture is necessary in the interest of justice.
“I will, however, limit the documents that are being sought.”