Prince Harry on Tuesday said he had suffered lifelong "press invasion" and accused some media of having blood on their hands, as he became the first royal in more than 100 years to give evidence in court.
Harry, 38, said he had been the victim of relentless and distressing media intrusion "most of my life up until this day" and attacked negative portrayals of him as the "spare to the heir".
"How much more blood will stain their typing fingers before someone can put a stop to this madness," the younger son of King Charles III added in a witness statement.
"You're then either the 'playboy prince', the 'failure', the 'dropout' or, in my case, the 'thicko', the 'cheat', the 'underage drinker', the 'irresponsible drug taker', the list goes on.
"As a teenager and in my early 20s, I ended up feeling as though I was playing up to a lot of the headlines and stereotypes that they wanted to pin on me... It was a downward spiral," he said, calling the reporting "utterly vile".
Harry is accusing Mirror Group Newspapers (MGN) Ltd -- publisher of The Mirror, Sunday Mirror and the Sunday People tabloids -- of illegal information gathering, including phone hacking.
During cross-examination by MGN's lawyer Andrew Green, Harry admitted that he had no recollection of reading the majority of the articles he had complained about.
But he called them "incredibly invasive" and taken as a whole they had made him acutely paranoid and ruined his relationships.
- 'Industrial scale' -
The case is Harry's latest legal battle with the press since he stepped down from frontline royal duties in early 2020 and relocated to California with his American wife Meghan.
The prince earned a rebuke from the judge on Monday for not turning up for the opening statement in his case as he had been attending his young daughter's second birthday on Sunday.
Dressed in a dark suit, the Duke of Sussex, as he is formally known, began giving evidence shortly after 0930 GMT after swearing an oath on the Bible.
On Monday, Harry's lawyer David Sherborne said that he was targeted by illegal information gathering even as a young schoolboy and his phone would have been hacked on "multiple occasions".
"No aspect of the young prince's life was safe" from press intrusion, he submitted.
The case against MGN centres on claims that its tabloids broke the law to obtain stories about Harry and other claimants, including two TV soap opera actors and the ex-wife of a comedian.
At the start of the trial on May 10, MGN apologised and admitted to "some evidence" of unlawful information gathering, including for a story about Harry.
But it denied voicemail interception and also argued that some claims had been brought too late.
Sherborne submitted that "industrial scale" illegal activities were happening at MGN and had been approved by senior executives.
- Legal battles -
Harry, who is fifth in line to the throne, has had a turbulent relationship with the press and holds the media responsible for the death of his mother Princess Diana, who died in a Paris car crash in 1997 while being pursued by paparazzi.
In television interviews and his explosive memoir "Spare", released in January, Harry hit out at other royals, accusing them of colluding with the press.
In court filings unveiled in April, Harry claimed the royal family as an institution had struck a "secret agreement" with one UK publisher that had prevented him from suing, to avoid a royal entering the witness box.
He also alleged the monarchy wanted to prevent the opening of a "Pandora's Box" of negative coverage that could tarnish the royal brand.
The prince has vowed to spearhead efforts to enforce change on Britain's tabloid behaviour.
He has also taken Associated Newspapers (ANL), publisher of the Daily Mail, to court over alleged breaches of privacy, and Rupert Murdoch's News Group Newspapers, which publishes The Sun.
The California-based prince made a surprise appearance at the High Court in March to hear legal arguments in the ANL case but did not give in-person evidence.
The last time a royal gave evidence in court was in the 1890s when the future king Edward VII took the stand in a slander trial.
Charles's sister, Princess Anne, became the first member of the current royal family to be convicted of a criminal offence after one of her dogs bit two children in 2002.
She pleaded guilty to an offence under the Dangerous Dogs Act so was not required to give evidence in court.