The publisher of the U.K. newspaper the Daily Mirror apologized to Prince Harry for unlawful gathering of information on his private life.

In court documents presented during the first day of the phone hacking trial, Mirror Group Newspapers admitted to one instance of unlawful gathering of evidence that occurred 20 years ago while Prince Harry was at a night club, reports Reuters.

Mirror Group Newspapers, which is owned by Reach, said it “unreservedly apologizes and accepts that (Harry) is entitled to appropriate compensation,” per CNN.

“(Mirror Group Newspapers) does not know what information this related to, although it clearly had some connection with his conduct at the nightclub,” the publisher added, admitting that the payment “represented an instruction to engage in (unlawful information gathering).”

The incident was initiated by a Mirror Group Newspapers journalist who hired a private investigator to illegally gather information on Prince Harry while he was at a London nightclub in 2004, according to People.

“(Mirror Group Newspapers) unreservedly apologizes for all such instances of (unlawful information gathering), and assures the claimants that such conduct will never be repeated,” the apology continued, per People.

The publisher denies the majority of allegations, arguing that some of the claims were made too late and that there is inadequate evidence of phone hacking.

Prince Harry and Meghan Markle’s ‘demands’ for attending the coronation — and the latest on a tabloid lawsuit

Why is Prince Harry suing Mirror Group Newspapers?

Prince Harry and several other public figures allege that Mirror Group Newspapers journalists unlawfully gathered private information on them through phone hacking, reports the BBC.

Harry and the other claimants allege that journalists from the Daily Mirror, Sunday Mirror and The People newspapers acquired undisclosed information on them through a slew of illegal methods.

The claimants believe that journalists accessed the voicemail of their targets by exploiting a gap in phone security. Listening to messages from friends and relatives provided the journalists with confidential information.

Journalists allegedly hired private investigators to trick people into providing them with confidential information, such as financial statements and medical records, reports the BBC.

The claimants called the journalist’s alleged information gathering methods “wrongdoing for cynical commercial reasons,” per the BBC.

According to Harry’s lawyer, David Sherborne, the claims against Mirror Group Newspapers — which span from 1995 to 2011 — are “significant not just in terms of time span but in the range of activity it covers,” per CNN.

Harry was victim to “intrusive methods of obtaining personal information,” Sherborne added, arguing that “no one should be subjected to that,” per CNN. The “unlawful methods” were “habitual and widespread” among journalists and editors, Sherborne said.

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

Harry blames the Mirror for his breakup with Chelsy Davy

Prince Harry believes his five-year on-and-off relationship with Chelsy Davy ended as a result of behavior from the Mirror.

Davy ended her relationship with Harry in 2009 after deciding that “a royal life was not for her” due to alleged harassment from the newspaper, reports the Independent.

Sherborne claimed that Harry “became immediately suspicious of anyone named in stories about him” and felt he could not trust anybody.

“It also caused great challenges in his relationship with his ex-girlfriend Chelsy Davy and made him fear for his and her safety,” Sherborne continued, per the Independent.

“They were never on their own, which ‘placed a huge amount of unnecessary stress and strain’ on their relationship,” Sherborne said. “Ultimately, (Mirror Group Newspaper’s) activities led Ms. Davy to make the decision that ‘a royal life was not for her’, which was ‘incredibly upsetting’ for Harry at the time.”

Harry is involved in multiple tabloid lawsuits

Harry is also suing the Daily Mail publisher Associated Newspapers.

Last year, Harry joined a group of several high-profile figures, including Elton John, to take legal action against Associated Newspapers. The lawsuit alleges that Associated Newspapers acquired information on high-profile figures through illegal means, according to CNN Business.

Some of the illegal activities listed in the allegations include: bugging phone calls, paying corrupt police to provide information, placing listening devices in the victims’ homes and cars, using deception to obtain medical records and hacking into bank accounts through “illicit means and manipulation,” per CNN.

Harry is also involved in a lawsuit against the publisher of the Sun newspaper — News Group Newspapers — over allegations of unlawful news gathering methods.

He claims that since he was a teenager, private investigators and journalists with the Sun intruded into his personal life through illegal means, per the BBC.

News Group Newspapers denies all claims.

Prince Harry’s war against The Daily Mail rages on — Elton John is joining him in the legal battle