Court documents, seen by the BBC, appear to show the Mail on Sunday will claim Meghan and other royals "rely on publicity about themselves and their lives to maintain their privileged positions".

The Duchess of Sussex launched a legal action against the Sunday newspaper in October last year alleging it unlawfully published a letter to her father.

The claim against the paper, filed at the High Court by law firm Schillings on behalf of the Duchess, alleged it and parent company Associated Newspapers misused private information, infringement of copyright and breach of the Data Protection Act 2018.

Prince Harry and Meghan Markle are stepping back from Royal duties.

The Mail on Sunday has always robustly defended the publication of the letter

In the public interest

According to the BBC, the court documents claim the duchess "did not have a reasonable expectation of privacy that the contents of the letter were private and would remain so", adding, "there is a huge and legitimate public interest in the Royal Family and the activities, conduct and standards of behaviour of its members.

The papers also say this extends beyond their public conduct to" their personal and family relationships because those are integral to the proper functioning of the monarchy."

In February, the Mail on Sunday published extracts of Meghan's handwritten letter to her estranged father Thomas Markle.

In one extract, published by the newspaper, the duchess wrote: "Your actions have broken my heart into a million pieces - not simply because you have manufactured such unnecessary and unwarranted pain, but by making the choice to not tell the truth as you are puppeteered in this. Something I will never understand."

'Manipulate readers'

When the legal action was announced in October, Prince Harry claimed the alleged unlawful publication of the private letter was done in "an intentionally destructive manner" to "manipulate" readers. He said he and his wife were forced to take action against "relentless propaganda.".

In a statement released at the time, a spokeswoman for law firm Schillings claimed the "intrusive" publication of the letter was part of Associated Newspaper's campaign to write "false and deliberately derogatory stories about" Meghan, "as well as her husband".

According to The Telegraph on Tuesday night, the Duchess of Sussex’s father is prepared to testify against her, and will side with the newspaper.

Reporting

But the Mail on Sunday is arguing the duchess did not "have a reasonable expectation of privacy that the contents of the letter were private and would remain so."

The 44-page legal defence by the newspaper says the duchess, while claiming she had not courted publicity for her relationship with her father, has not denied authorising her friends to speak about it for an article in a US publication.

It claims printing excerpts from the letter did not breach her copyright as it was not not a protected "original literary work" but a setting out of existing facts. They also argue there was no infringement of Meghan's data rights as the subject matter was not sensitive and about topics she had already put in the public domain.

It also denied selectively editing the letter, insisting it accurately reflected the tone and meaning of the letter's contents.

This article first featured on our sister site the i.

'Royals rely on publicity': Mail on Sunday to defend publishing Meghan Markle's letter to father