The admission was made in court filings outlining Mirror Group Newspapers’ defense.

The group continued to deny that it hacked phones to intercept voicemail messages, and said that Harry and three less-well-known celebrities brought their claims beyond a time limit.

But it acknowledged there was “some evidence of the instruction of third parties to engage in other types of UIG (unlawful information gathering) in respect of each of the claimants,” which includes the Duke of Sussex. It said this “warrants compensation” but didn’t spell out what form that might take.

“MGN unreservedly apologizes for all such instances of UIG, and assures the claimants that such conduct will never be repeated,” the court papers said.

The publisher said its apology was not a tactical move to reduce damages but was done “because such conduct should never have occurred.”

The trial is Harry’s opening salvo in his legal battle against the British press. Harry and the other celebrities are suing the former publisher of the Daily Mirror for alleged invasion of privacy.

The case is the first of the duke’s three phone hacking lawsuits and threatens to do something he said his family long feared: put a royal on the witness stand to discuss embarrassing revelations.

The activities in question stretch back more than two decades, when journalists and private eyes intercepted voicemails to snoop on members of the royal family, politicians, athletes, celebrities and even crime victims. A scandal erupted when the hacking was revealed.

Harry is expected to testify in person in June, his lawyer has said. It won’t be his first time in the High Court, following his surprise appearance last month to observe most of a four-day hearing in one of his other lawsuits.

He did not show up for opening statements in the trial. Harry breezed through London for Saturday’s coronation of his father, King Charles III, before leaving immediately after the ceremony to fly back to California to be with his family for his son’s birthday.

The prince has waged a war of words against British newspapers in legal claims and in his best-selling memoir “Spare,” vowing to make his life’s mission reforming the media that he blames for the death of his mother, Princess Diana. She died in a car wreck in Paris in 1997 while trying to evade paparazzi.

Harry has also sued the publishers of the Daily Mail and The Sun over the phone hacking scandal that metastasized after a year-long inquiry into press ethics in 2011 revealed that employees of the now-defunct News of the World tabloid eavesdropped on mobile phone voicemails.

Harry has outlined his grievances against the media in court papers, saying the press hounded him since his earliest days and created a narrative that portrayed him as “the ‘thicko,’ the ‘cheat,’ the ‘underage drinker.’” His relationships with girlfriends were wrecked by “the entire tabloid press as a third party.”

“Looking back on it now, such behavior on their part is utterly vile,” he said in a witness statement in a similar case.

His lawsuits could further roil family relations that have been strained since Harry and his wife, Meghan, left royal life in 2020 and moved to the United States after complaining about racist attitudes from the British press.

Mirror Group Newspapers and other publishers have primarily defended themselves by asserting that Harry failed to bring his cases within a six-year year time limit. The duke’s lawyer has argued that an exception should be applied because publishers actively concealed the skullduggery.

In a stunning revelation last month that dredged up an embarrassing chapter in his father’s life, Harry blamed his delay in bringing suit, in part, on his family.

He asserted he was barred from bringing a case against The Sun and other newspapers owned by media magnate Rupert Murdoch because of a “secret agreement” — allegedly approved of by Queen Elizabeth II — that called for reaching a private settlement and getting an apology.

“The reason for this was to avoid the situation where a member of the royal family would have to sit in the witness box and recount the specific details of the private and highly sensitive voicemails that had been intercepted,” Harry said in a witness statement against News Group Newspapers.

“The institution was incredibly nervous about this and wanted to avoid at all costs the sort of reputational damage that it had suffered in 1993,” he said, alluding to a transcript of a leaked recording — published in the Sunday Mirror — of an intimate conversation his father, then Prince of Wales, had with his paramour, now Queen Camilla, in which he compared himself to a tampon.

Harry said his brother, Prince William, had quietly settled his own hacking claims with News Group for “huge sum of money” in 2020. He also claimed his father had directed palace staff to order him to drop his litigation because it was bad for the family.

Murdoch’s company denied there was a “secret agreement” and wouldn’t comment on the alleged settlement. The palace hasn’t responded to requests for comment.

Harry has alleged that reporters at the Daily Mirror, Sunday Mirror and Sunday People used illegal methods to gather material from his family and friends for nearly 150 articles. The newspaper has said he is wrong about how its reporters got information, saying they used legal methods for many articles.

In 2015, publishers of The Mirror printed a front-page apology for phone hacking and tripled its fund to 12 million pounds ($15 million) to compensate victims.

Mirror Group said more than 600 of some 830 claims had been settled. Of the remaining 104 cases, 86 were brought too late to be litigated, it said in court papers.

“Where historical wrongdoing has taken place, we have made admissions, take full responsibility and apologize unreservedly,” a spokesperson for Mirror Group Newspapers said in advance of the trial. “But we will vigorously defend against allegations of wrongdoing where our journalists acted lawfully.”

The lawsuits were combined as a test case that could determine the outcome of hacking claims also made against Mirror Group by former Girls Aloud member Cheryl, the estate of the late singer George Michael, and former soccer player Ian Wright.