Prince Harry has appeared in a UK court. Here's what we know about his historic testimony

Prince Harry has become the first senior royal to appear in a witness box in more than a century in a lawsuit brought against Mirror Group Newspapers.

Prince Harry alleges that journalists at the Daily Mirror and its sister papers used unlawful techniques on an "industrial scale" to get scoops. Publisher Mirror Group Newspapers is contesting the claims. Source: AP / Alberto Pezzali

Key Points

• Prince Harry is the first senior royal to appear in a witness box in the United Kingdom in more than a century.
• The prince and 100 others are suing Mirror Group Newspapers over allegations of widespread unlawful information gathering.
• Harry said the press would try to destroy his relationships with girlfriends, blaming them for his break-up with Chelsy Davy.

Prince Harry has launched a fierce attack on the "vile" press, blaming tabloids for destroying his adolescence and later relationships, as he gave evidence for almost five hours in his lawsuit against a tabloid publisher.

As he became the first senior royal to appear in a witness box in the United Kingdom in more than a century, Harry also said the thought of people unlawfully intruding into the private life of his late mother Princess Diana made him "feel physically sick".

Here's what you need to know about Harry's historic testimony.

Who is Prince Harry suing and why?

The prince, the fifth-in-line to the throne, and 100 others are suing Mirror Group Newspapers (MGN) - the publisher of the Daily Mirror, Sunday Mirror and Sunday People - at the High Court in London over allegations of widespread unlawful information gathering between 1991 and 2011.

What is the Prince alleging?

In his 50-page written witness statement and a day of cross-examination from MGN's lawyer Andrew Green, the younger son of King Charles said he had been targeted since 1996 when he was a schoolboy.

Harry said the press would try to destroy his relationships with girlfriends, blaming them for his break-up with Chelsy Davy, for causing his circle of friends to shrink and for bouts of depression and paranoia.

He said he had been labelled a "playboy prince", a "thicko", a "failure" and a "drop out".

Britain's Prince Harry leaves the High Court in London. Prince Harry has given evidence over the phone hacking trial against the Mirror Group Newspapers. The Duke of Sussex is seeking damages against the Daily Mirror over unlawful information gathering through phone hacking. Source: EPA / Tolga Akmen

"Looking back on it now, such behaviour on their part is utterly vile," he wrote, saying the tabloids had incited "hatred and harassment" into his and his wife Meghan's private lives.

In another section he said: "How much more blood will stain their typing fingers before someone can put a stop to this madness?"

Asked to whom he was referring, he said: "Some of the editors and journalists that are responsible for causing a lot of pain, upset and in some cases - perhaps inadvertently - death."

What did Mirror Group's lawyer say?

Mr Green began his questioning on Tuesday respectfully, personally apologising to Harry on MGN's behalf over one instance in which it admitted unlawful information gathering, saying "it should never have happened and it will not happen again".

The lawyer then forensically and with increasing hostility quizzed the prince over 33 newspaper articles, whose details Harry claims were obtained unlawfully.

Looking relaxed but serious, and speaking softly but firmly, Harry said thousands if not millions of stories had been written about him as Mr Green pressed him on whether he had read the MGN articles in question at the time they were published.

The lawyer intimated that the distress he had suffered was caused by press coverage in general, not the specific MGN stories, and suggested they were based on details already in the public domain.

Court artist sketch of Prince Harry being cross-examined during the phone hacking trial against Mirror Group Newspapers (MGN).. Source: AAP / Elizabeth Cook/PA/Alamy

On a number of occasions, Mr Green described his allegations as "total speculation".

When asked about the source of information for articles at the centre of his lawsuit, Harry repeatedly said that question should be asked of the journalist who wrote them, saying they appeared suspicious.

Quizzed about one article, Harry said it was "as distressing looking at it now" as it was at the time it was published in 2004.

What happens next?

Prince Harry will be back on Thursday to give more evidence.

"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," Harry said in his statement.

MGN, now owned by Reach, has previously admitted its titles were involved in phone-hacking, settling more than 600 claims, but Green has said there was no evidence that Harry had ever been a victim.

He argued that some of the personal information had come from, or with the consent of, senior Buckingham Palace aides.

Harry, who has accused his family, or their aides of colluding with the tabloids, replied: "From certain individuals, yes."