LONDON (AP) — The British publisher of the Daily Mirror apologised for one instance of snooping on Prince Harry but denied his other claims Wednesday, as a trial for one of Harry’s phone hacking lawsuits began with the prince’s lawyer accusing the newspaper of unlawfully gathering information on “an industrial scale.”

The admission that the publisher employed a private investigator for a 2004 article headlined “Sex on the beach with Harry” may only give the Duke of Sussex a taste of satisfaction, though. Since the story in question wasn’t one of the nearly 150 that Harry alleges resulted from skulduggery, the disclosure may have little bearing on the verdict.

The seven-week trial that opened in London is Harry’s biggest test yet in his legal battle against the British media. He and three others, including two soap opera actors, are suing Mirror Group Newspapers for alleged misuse of private information between 1991 and 2011.

The prince wasn’t in court as his attorney, David Sherborne, began his opening statement, saying unlawful acts were “widespread and habitual” by reporters and editors at the Daily Mirror, Sunday Mirror and Sunday People.

“It was a flood of illegality,” Sherborne said. “But worse, this flood was being approved by senior executives, managing editors and members of the board.”

Invoices and phone records — some so old they came from obsolete Palm Pilots — showed how the news, entertainment, sports, and photo departments relied on investigators plying unscrupulous tactics.

Sherborne said that former Daily Mirror editor Piers Morgan was aware of the hacking and even participated. Morgan has publicly denied involvement in phone hacking.

The allegations go back to a scandal that erupted over journalists and private eyes who intercepted voicemails for scoops on members of the royal family, politicians, athletes, celebrities and even crime victims. It evolved from a low-tech hack of punching in default passwords in the early days of voicemail to using deception to gain medical records, tapping phones and bugging homes.

Publisher Mirror Group Newspapers denied that it hacked phones to intercept voicemail messages of Harry and the three others and it said they had brought their claims well past a six-year time limit.

But in court papers outlining its defence, the publisher acknowledged “some evidence of the instruction of third parties to engage in other types of UIG (unlawful information gathering).” It said that the activity “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 company said its apology wasn’t a tactical move to reduce damages, but was done “because such conduct should never have occurred.”