The Duke of Sussex is one of several high-profile claimants accusing Associated Newspapers Limited (ANL) of using unlawful information-gathering methods.
It is alleged that the publisher hired private investigators to place listening devices in cars, intercept private calls, and improperly access personal records.
Harry is expected to give evidence in court next Thursday, with his appearance scheduled to last a full day.
According to a draft trial timetable.
The group bringing the claim includes Sir Elton John, Baroness Doreen Lawrence, Sir Simon Hughes, Sadie Frost, and Liz Hurley.
Other claimants are also expected to give evidence during the nine-week trial, which is due to begin on Monday.
Claimants allege unlawful activities.
During a preliminary hearing, the group’s lawyers challenged sections of ANL’s proposed opening arguments.
Their concerns focused on references to an alleged “scheme of camouflage,” which the claimants said amounted to unfounded allegations of fraud and professional misconduct.
David Sherborne, barrister for the claimants, said: “The allegations made by the defendants are exceptionally serious, of fraud, dishonesty, and professional misconduct.
“They cannot be introduced by assertion in opening written submissions and are not simply commentary on pleaded issues.
“The allegations made by the defendants are not confined to the credibility of witnesses, as above, the defendant explicitly seeks findings, and also asserts as a fact that actions amount to a ‘calculated attempt to withhold the true position from the court’.”
Antony White KC, representing ANL, argued that the statements reflected concerns about the credibility of witnesses rather than formal accusations requiring amendment.
He said: “It is not necessary to plead a case if the other side’s witnesses are not telling the truth.”
However, Mr Justice Nicklin ruled that ANL must amend its trial opening note.
He said: “In my judgment, the camouflage scheme that is relied upon by the defendants goes far further than an attack on credibility.
“It seems to be that the requirements of fairness mean that the defendant must seek to amend its defence.”
Mr White indicated that he would condense the disputed material in the opening note.
The hearing before Mr Justice Nicklin is due to conclude on Thursday.
The trial will examine detailed allegations of phone-tapping, data “blagging,” and the use of private investigators.
