The Duke of Sussex lost friendships “entirely unnecessarily” due to the “paranoia” caused by alleged unlawful information gathering, the High Court has been told as part of his case against the Daily Mirror’s publisher.

On Tuesday, Harry appeared in a witness box in the Rolls Building to face cross-examination by a barrister for Mirror Group Newspapers (MGN) as part of his claim over alleged unlawful activities, including phone-hacking.

The 38-year-old told the court that MGN’s alleged intrusion into his life contributed to “a huge amount of paranoia” in his relationships.

In his witness statement, the duke said that he found it “very hard to trust anyone, which led to bouts of depression and paranoia”.

“Friendships were lost entirely unnecessarily,” he added.

Harry continued: “As I am uncovering the extent of the unlawful activities carried out by MGN’s journalist (sic) and senior executives towards me, I feel somewhat relieved to know that my paranoia towards my friends and family had, in fact, been misplaced, although feel sad for how much it impacted my adolescence.”

The duke later said in his statement that he can now see “how much of my life was wasted on this paranoia”.

He added: “I’ve always heard people refer to my mother as paranoid, but she wasn’t.

“She was fearful of what was actually happening to her and now I know that I was the same.”

MGN phone hacking trial
The Duke of Sussex arrived at the Rolls Buildings in central London for his cross-examination (Jeff Moore/PA)

The court also heard:

– Harry described the state of the British press and the Government as both being at “rock bottom”, with the Government having “no appetite” for press regulation;

– The duke suggested newspaper stories about rumours his father was instead James Hewitt, a former lover of Diana, Princess of Wales, were aimed at ousting him from the royal family;

– He was “extremely worried” he was going to be expelled from Eton following press reports that he was using drugs;

– The duke was singled out as a “pussy” by his peers following press reports of his injuries during his time at school and Sandhurst;

– Harry alleged that both he and the Duchess of Sussex “have been subjected to a barrage of horrific personal attacks and intimidation from Piers Morgan”, the former Mirror editor;

– The duke said some editors and journalists are “responsible for causing a lot of pain, upset and in some cases, speaking personally, death”.

Harry is suing MGN for damages, claiming journalists at its titles, which also include the Sunday Mirror and Sunday People, were linked to methods including phone hacking, so-called “blagging” or gaining information by deception, and use of private investigators for unlawful activities.

He alleges that about 140 articles published between 1996 and 2010 contained information gathered using unlawful methods, and 33 of these have been selected to be considered at the trial.

Andrew Green KC, for MGN, asked Harry about part of his case which states that he was caused particular distress “because he is a very private person” and was in the public eye at a young age.

The duke told the court: “I believe that as a child, every single one of these articles played an important role in my growing up.”

However, he added that he could not confirm whether he remembered reading specific articles at the time they were published, adding that there were “millions” of articles “that have been written about me since age 12”.

Referring to an article which reported that the duke and his brother were going rock climbing rather than attending a gala for the late Queen Mother, Mr Green asked Harry if it was his case that came from unlawful voicemail interception.

The barrister asked whose phone the duke believed was hacked in order to get that information, with Harry replying that “it could have been anyone, from myself, my brother” or two other people.

Asked which information he thought had been obtained unlawfully, Harry said: “There’s quite a lot of aspects, quotes and information in there, not to mention a large part of the reason we were going rock climbing 270 miles away was to get away from press intrusion.”

MGN phone hacking trial
Dozens of journalists attended Tuesday’s hearing (Jeff Moore/PA)

The duke later said he knew how “desperate journalists were for anything royal”, adding it was a “competition” between newspapers for “any element of our private lives that is interesting to the public”.

Harry’s claim is being heard alongside three other “representative” claims during a trial which began last month and is due to last six to seven weeks.

MGN is contesting the claims and has either denied or not admitted each of them.

The publisher also argues that some of the claimants have brought their legal action too late.

Harry’s court appearance comes just over a month after he attended the coronation of his father, the King.

It is thought to be the first time a senior member of the royal family has personally appeared in court proceedings since 2002, when the Princess Royal pleaded guilty to a charge under the Dangerous Dogs Act after her pet bit two children in Windsor Great Park.