Diana, Princess of Wales, gave a royal phone book to the News of the World in order to "take on" her estranged husband, the Old Bailey has heard.
Former NoW royal editor Clive Goodman told the phone-hacking trial he was sent the 1992 book because she was looking for "an ally" in the press, the BBC reports.
He said the late princess wanted to show the Prince of Wales there "were forces that would rage against him".
Mr Goodman is accused of paying police for royal phone books, which he denies.
'Difficult time'
Princess Diana, who separated from her husband in 1992 after 11 years of marriage, sent the book to the newspaper and it "worked its way into my pigeonhole", said Mr Goodman.
"She was going through a very, very difficult time," he told the court.
"She told me she wanted me to see the scale of her husband's staff and household, compared with others.
"She felt she was being swamped by people close to his household.
"She was looking for an ally to take him on - to show there were forces that would rage against him."
Mr Goodman said the princess later called him to check he had received it.
Princess Diana and Prince Charles divorced in 1996. She was killed in a car crash in Paris a year later.
The book was "one of a number that came to me over a number of years", said Mr Goodman, who denies conspiracy to commit misconduct in a public office.
Asked if any of the books came from public officials, he said: "No, not one of them."
'Aggressive and combative'
Mr Goodman, 56, of Addlestone in Surrey, was made royal editor in 2000, the court heard.
But he told the Old Bailey his position was "downgraded" from 2003 because of his poor relationship with several key desk editors, some of whom cannot be named for legal reasons.
He said one, deputy editor Neil Wallis, was aggressive and "didn't like me".
Mr Wallis, he said, influenced the then editor Andy Coulson, and as a result: "[Mr Coulson] became more aggressive, more combative and more bullying."
Mr Goodman said Mr Coulson moved his stories down the list of those being discussed at the paper's editorial conferences.
"He took me off the list altogether. I was forever being berated for the lack of quality of my stories," he said.
The jury has previously been told of Mr Goodman's 2007 conviction for phone hacking.
Asked by his barrister David Spens QC if he ever used information in a green book for hacking purposes, he responded "No."
The court also heard News International, the owner of the Sunday tabloid paper, paid Mr Goodman £140,000 - the equivalent of a year-and-a-half's salary - after he was dismissed.
'Worried for you'
Earlier, the court heard from the mother of former NoW editor and ex-NI chief executive, Rebekah Brooks.
Deborah Weir told the court her daughter Mrs Brooks urged her not to watch the news as it emerged that murdered schoolgirl Milly Dowler's phone had been hacked.
In one of a series of text messages sent by Mrs Weir to her daughter, she said: "I'm so worried for you."
Mrs Brooks, who is among the seven defendants on trial, denies conspiracy to hack phones, conspiracy to commit misconduct in public office, and two counts of conspiring to pervert the course of justice.
