Kensington Palace is considering taking legal action over a leaked letter from the Duchess of Sussex to her father, as her estranged family threaten to make public further details of their relationship breakdown.
The five-page letter, which laid bare the Duchess' feelings over her father's behaviour since she married into the Royal Family, was shared by Thomas Markle with a newspaper this weekend and has since been published around the world.
Palace aides are understood to be considering whether to take a stand over the very public family disclosures, taking legal advice before the Duchess decides whether she wishes to take formal action.
The Duchess' estranged half-sister has said her father "is prepared to release more" of the letter, while her half-brother Thomas Jr said the father-daughter relationship was now "broken beyond repair".
Under UK law, the Duchess owns the copyright of the handwritten letter, which was published in a Sunday newspaper days after five friends of the Duchess shared details of its existence for the first time in an interview with US celebrity magazine People.
The friends, who would have been immediately recognisable to the Duchess after giving details of their visits to stay with her, disclosed she had told him in writing: 'Dad, I'm so heartbroken, I love you. I have one father. Please stop victimising me through the media so we can repair our relationship.'"
One friend continued: "He writes her a really long letter in return, and he closes it by requesting a photo op with her.
"And she feels like, 'That's the opposite of what I'm saying. I'm telling you I don't want to communicate through the media, and you're asking me to communicate through the media'."
Thomas Markle, 74, responded by showing the letter to the Mail on Sunday, which published emotional excerpts in which the Duchess accused him of misrepresenting his behaviour and detailing her distress.
Telling them he had felt the way the letter was presented in People magazine "vilified" him, he said: "It was presented as her reaching out and writing a loving letter in the hope of healing the rift, but the letter isn't like that at all. I have the right to defend myself."
Kensington Palace have not yet commented on whether the "five friends" interview had been conducted with the tacit blessing of the Duke and Duchess of Sussex, or with the knowledge of their staff.
The Royal houses have taken legal action on numerous occasions in recent history, both using injunctions to prevent the publication of personal details and suing for breach of copyright.
In 2006, the Prince of Wales won a privacy case after the court of appeal ruled the Mail on Sunday had infringed his copyright and confidentiality by publishing extracts from his 1997 Hong Kong diaries.
In the 1980s, the Sun made a payment to charity and apologised for publishing a letter from the Queen and Duke of Edinburgh about Prince Edward's decision to leave the Royal Marines. In 1993, the paper settled a breach of copyright case over a leaked copy of the Christmas speech with a payment to charity.
Fans of the Duchess, who follow her activities online and voice strong opinions through social media, have recently criticised the palace for "failing to protect" her from what they perceive to be negative coverage.
Shortly after their relationship was made public, Prince Harry issued an extraordinary statement complaining about the press attention on her life, saying he "is worried about Ms. Markle's safety and is deeply disappointed that he has not been able to protect her".
She, along with the Duchess of Cambridge, have recently suffered from extreme written abuse on social media, with palace staff spending hours deleting comments from their Instagram page.
Omid Scobie, a correspondent for US television show Good Morning America, which was privy to the People story ahead of publication, said: "While the purpose of Meghan's letter was very much to repair the relationship with her father, she knew in her heart of hearts that this was going to be released to the papers.
"Thomas has a record of this and this is exactly the man that she knows.
"So, many of the things in that letter were written with the public in mind. She very much wanted to set the record straight.
"The letter being out there puts the story very much in the past, and she's focused on the present." Kensington Palace declined to comment.