The Duke of Sussex has denied using the pseudonym “Mr Mischief” to communicate with a tabloid journalist via Facebook.

As he gave evidence inhis privacy claim against Associated Newspapers Limited, the publisher of the Daily Mail, it was put to the Duke that he had met the Mail on Sunday’s diary editor at a house party in Ibiza in 2011 or 2012, “socialising” with her there and in London.

The High Court heard that Prince Harry had added Charlotte Griffiths as a friend on Facebook using the name “Mr Mischief”. He was said to have given her his mobile number, with the pair exchanging “friendly messages”.

He denied the claim, telling the court: “I have never used the name ‘Mr Mischief’” and saying that he had only been to Ibiza once, with his wife and son.  He admitted meeting Ms Griffiths at a party hosted by his friend Arthur Landon, but said he had “cut off contact” when he found out who she was.

The Duke, Sir Elton John and his husband David Furnish, the campaigner Baroness Lawrence, the former MP Sir Simon Hughes and the actresses Sadie Frost and Liz Hurley are all bringing legal action against Associated Newspapers Limited over alleged unlawful information-gathering.

The publisher has called their accusations “preposterous smears” and insisted its journalists had legitimate sources including the claimants’ friends and acquaintances.

The Duke’s claim hangs on 14 articles published between 2001 and 2013, many concerning his relationship with Chelsy Davy, his long-term former girlfriend.

Within moments of taking the oath, he was arguing against evidence being put to him by Antony White KC, Associated’s barrister. “For the avoidance of doubt, I’m not friends with any of these journalists and never have been,” he said. “My social circles were not leaky. ⁠I ‌want to make that absolutely ‍clear.”

He had been “forced to perform” for journalists he loathed, he said, “knowing who they are and knowing full well the kind of stories they had written about me and how they have commercialised my private life”.

Asked why he had not complained about the relevant articles at the time of their publication, the Duke told the court that the Royal family “had a never complain, never explain policy”, meaning to do so would have been “very hard”.

He spent just under two hours on the witness stand, setting out why he believed a series of stories published in the Daily Mail or the Mail on Sunday had been obtained through phone hacking and other unlawful means. Mention of the Duchess of Sussex made him emotional. “They have made my wife’s life an absolute misery, My Lord,” he said, his voice cracking.

Asked by David Sherborne, his barrister, how he felt about the conduct of Associated, the Duke said his life had been treated as “open season” and “commercialised by these people”.

He rejected the notion that to act in the public interest was to interest the public, calling the idea that he had no right to privacy “disgusting”.

“I think it is fundamentally wrong to have to put all of us through this ‍again when all we were asking for is an apology and some accountability,” he said. “It is a horrible experience, and the worst of it is that by sitting up here and taking a stand against them… they continue to come after me.”

In his 23-page witness statement, Prince Harry described how “paranoia and distrust builds up” and “very quickly turns into a nightmare”.

He said he had become “increasingly troubled” by the “never complain, never explain” approach to the press when his relationship with Meghan became public.

The Mail, he added, had been the first newspaper to publish Ms Davy’s name. “From that point onward, everything blew up and her life as she knew it was over – her ability to enjoy some semblance of privacy evaporated instantly,” he said.

To prove that “so-called sources” had got their facts wrong, he noted that one had referred to him drinking a beer and a glass of wine, and said: “I do not drink wine.”

The Duke said Queen Elizabeth II, his late grandmother, had never allowed his girlfriends to join the Royal family at Christmas, and that he had not followed the Leveson Inquiry into press ethics.

He said it was a “misconception” that he family was in “constant communication” and, as such, he had no idea who might have brought legal claims against tabloid newspapers.

Asked about his knowledge of the campaign group Hacked Off, he said he had only become aware of it “in the last four or five years”, adding: “I happen to think they do fantastic work, Mr White.” Associated’s barrister replied: “I am pleased to hear it.”

The Duke was rebuked by Mr Justice Nicklin for arguing with allegations put to him, and was told: “Part of Mr White’s job is to put allegations to you. This is a big moment. You are doing exactly what lots of litigants do – you tend to argue back about what he is putting to you.”

Prince Harry did not “have to bear the burden of arguing the case”, the judge added, saying that was a job for his barrister. Later, he told him he should not feel under pressure to argue specific points, but should just “answer the questions”.

The Duke insisted he did not feel under pressure and simply wanted the judge to “have an idea of what it is like living in this world” under “24-hour surveillance”.

Harry had arrived in the courtroom shortly before 11.30am, clutching a bottle of water. When the judge took his seat, Mr Sherborne said: “With My Lord’s permission, I call my first witness, the Duke of Sussex.”

A clerk asked for silence as Harry held a small black bible aloft in his right hand to take the oath.

“Before we start, can I just ask you how you would prefer to be called in these proceedings?” Mr Sherborne said. “How do you want to be addressed?” With a smile, the Duke replied: “Same as last time, please.”

The trial, scheduled to last nine weeks, has a long way to go – but the Duke is confident and appeared buoyed by his performance. After leaving the court, he said: “Today we reminded the Mail Group who is on trial and why.”

His spokesman added: “Today’s cross-examination was revealing in its weakness – assertive in tone, but collapsing immediately under scrutiny from Prince Harry.”

The Duke will attend court again on Thursday, with the spokesman saying he would do so “to support, and show solidarity with, the other claimants”.

A spokesman for Associated said: “It is for the judge to decide what he makes of a witness’s evidence – not Prince Harry or his spokesman – and naive and self-serving statements during the trial are inappropriate.”

Associated is a subsidiary of Daily Mail and General Trust, Lord Rothermere’s holding company, which has agreed to acquire The Telegraph for £500m. The impact of the proposed takeover on competition and the public interest will be investigated.