Britain's Prince Harry has told the High Court in London it is "disturbing to feel that my every move, thought or feeling was being tracked" so the publisher of the Daily Mail could "make money out of it".
Harry, Elton John and his husband David Furnish, campaigner Doreen Lawrence, politician Simon Hughes, and actresses Sadie Frost and Elizabeth Hurley all allege Associated Newspapers Limited (ANL) had a practice of "clear systematic and sustained use of unlawful information gathering".
Lawyers acting on behalf of the claimants said ANL "knew they had skeletons in their closet" when they emphatically denied all claims of unlawful practices.
In written submissions on behalf of the Duke of Sussex, barrister David Sherborne said ANL's methods of information-gathering left him "paranoid beyond belief" and created a "massive strain" on personal relationships.
Prince Harry, who is expected to give evidence on Thursday, was in court to follow proceedings.
Mr Sherborne said the alleged unlawful information gathering in his case is related to 14 articles between 2001 and 2013.
Mr Sherborne's submissions include Harry's words, which say: "I find it deeply troubling that Associated used phrases such as 'sources', 'friends' and the like as a device to hide unlawful information-gathering."
The barrister continues: "The Duke of Sussex has been caused great distress by each and every episode of unlawful information gathering against him by Associated or on its behalf, and the fruits of that unlawful information gathering in the 14 unlawful articles of which he complains."
He adds: "It is evident from the articles and the evidence of the Duke of Sussex that the targeting of him has had a profoundly distressing effect, with episodes of pleaded unlawful information gathering described as 'disturbing to feel that my every move, thought or feeling was being tracked and monitored just for the Mail to make money out of it', 'intrusion (that) was terrifying' for loved ones, creating a 'massive strain' on personal relationships while invidiously 'creating distrust and suspicion', and 'driving me paranoid beyond belief, isolating me'."
In response to Harry's claims, ANL said in their written submissions: "At all material times, the Duke of Sussex's social circle was and was known to be a good source of leaks or disclosure of information to the media about what he got up to in his private life."
Antony White KC, for ANL, said Harry had discussed his private life in the media, while information about his life was also provided by Palace spokespeople.
Opening the trial in the legal action against ANL, which publishes the Daily Mail and the Mail on Sunday, Mr Sherborne said its denials of unlawful activity "were not true".
The barrister said the alleged acts "involved journalists from both the Daily Mail and Mail on Sunday and every significant editorial desk".
Mr White said it was "a striking feature of the case that none of the articles were the subject of complaint by the claimants at the time of publication".
He told the court in written submissions that the celebrities bringing legal action had "leaky" social circles and that all of the claims have been brought too late.
He said: "In relation to almost every article alleged to be the product of phone hacking or phone tapping, Associated is able to call a witness or witnesses to explain how the article was in fact sourced.
"The claimants' inferential case of phone hacking and phone tapping is met and convincingly rebutted.
"The pattern of misconduct the claimants seek to establish is simply not made out."
The claimants allege in their written submissions the publisher had a "culture of unlawful information gathering that wrecked the lives of so many".
Mr Sherborne told the court the Daily Mail and Mail on Sunday were engaged in unlawful information-gathering over "at least two decades".
He added: "There is evidence, indisputable evidence, in the documents that Associated journalists and senior executives were commissioning and approving the acquisition and use of unlawfully obtained information, and they must have known that.
"That is why we say this was no clean ship, far from it."
Elton John and Mr Furnish followed proceedings on a live video-link, while some of their co-claimants were in court.
The claimants allege the publisher carried out or commissioned unlawful activities such as hiring private investigators to place listening devices inside cars, "blagging" private records and accessing private phone conversations.
ANL has strongly denied wrongdoing.
The claimants started their legal cases against ANL in 2022, with documents setting out the claims naming dozens of journalists, including some national newspaper editors.
In 2023, ANL failed to have the cases thrown out before a trial on the basis that they were "time-barred" or brought too late.
Mr Sherborne previously said the alleged unlawful acts in the claim include illegally intercepting voicemail messages, listening to live landline calls and obtaining medical records.
In written submissions, he said: "They range through a period from 1993 to 2011, even continuing beyond until 2018."
Prince Harry has previously brought legal action against other newspaper publishers over allegations of unlawful information gathering.
He was previously awarded £140,600 in damages by a judge from Mirror Group Newspapers in 2023, and settled a claim against News Group Newspapers, the publisher of the Sun and the now-defunct News Of The World, last January.
The trial, which is expected to last nine weeks, continues.
