Finding Freedom author Omid Scobie testified on the fourth day of the Duke’s hearing against a British group of newspapers in the High Court in London.
The journalist has told the High Court he learned of "immoral" phone hacking at Mirror Group Newspapers (MGN) while he was doing work experience there.
Meghan's pal entered the witness box on Monday to give evidence in the seven-week long trial involving the unlawful gathering of information from high-profile figures including Prince Harry, saying he himself has never listened to private voicemails.
Scobie has told the court that he does not have a personal relationship with Harry or Meghan.
The author, who is considered Meghan's pal, also told the court he had never socialised with Prince Harry after he was asked whether he had a "vested interest" in representing the Duke and Duchess of Sussex in a good light to advance his career.
"I don't have a close relationship [with the Duke and Duchess] personally," Scobie insisted when Green questioned him whether he referred to his "close relationship" with them in his witness statement.
"It's got to the point that when I get press releases from Harry and Meghan's people, I wait for other people to post it first so I don't have to deal with the Daily Mail articles saying that it came from me," he added.
Scobie has said it is "fair" to say the treatment of the Sussexes in the couple's Finding Freedom biography was favourable.
He was asked whether his "sympathies" lie with the couple but denied that was the case: "Not necessarily I think I’ve had, especially earlier on, deeper insights and access to sources that others haven’t."
"I haven’t only leant on palace aids and sources for information," he told the High Court.
Scobie continued: "I don't know the Duke on that level, I don't have his phone number, I've never socialised with him before," adding that his testimony was going to make his life "more difficult".
“What I’m doing here today is actually making my life more difficult," he told the court, referring to his being branded as the couple's "mouthpiece" and "cheerleader" by other news publications.
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