The Mail on Sunday can now rely on the recent biography of the Duke and Duchess of Sussex in its defence to Meghan’s High Court privacy claim over the publication of a letter to her estranged father.

The Duchess of Sussex, 39, is suing the newspaper’s publisher, Associated Newspapers (ANL), over privacy infringement for publishing the private correspondence to her father, Thomas Markle.

In the latest stage of the process, ANL sought permission to extend their defence on the basis that Meghan had “lost her rights to privacy in the contents of the letter” because “she and her husband cooperated with the authors” of Finding Freedom to put out “their version of events”. 

A spokesperson for the couple told The Independent on numerous occasions that they were not involved and that Finding Freedom was based on co-authors Omid Scobie and Carolyn Durand’s own experiences in the royal household.

On 21 September, Meghan’s defence team stated that the couple did not meet with the authors “for the purposes of the book” and that Meghan’s PR representative was not given the book beforehand to suggest proposed changes to the text.  

On Tuesday, Meghan’s lawyers said accusations the duke and duchess “collaborated” with the authors was a “conspiracy theory” and argued that references to the letter in the book were simply “extracts from the letter lifted from the defendant's own articles”.

But, ruling on ANL’s application, Judge Francesca Kaye allowed the publisher to amend its defence and said doing so did not raise “new defences”, but simply added “further particulars” of ANL's case.

ANL wholly denies the allegations, particularly that the letter was edited in any way that changed its meaning.

A spokesperson for Schillings, who are acting on The Duchess’s behalf, told The Independent on Tuesday: “The Court has today stated that The Mail on Sunday will be allowed to amend its legal defence for trial regardless of whether that defence is accurate or true, which based on legally sworn witness statements refuting the newspaper’s arguments, it is not. 

“The Mail has been allowed to prolong this action and try contending its amended defence at trial, where we have no doubt it will fail. This defence has no merit and is in fact false.

“This latest hearing was unfortunately another step in a case that has already been drawn out by a defendant who uses the legal process to exploit The Duchess’s privacy and the privacy of those around her for profit-motivated clickbait rather than journalism. As a reminder, it is The Mail on Sunday and Associated Newspapers who acted unlawfully and are the ones on trial, not The Duchess of Sussex, although they would like their readers to believe otherwise.”

In a preliminary hearing in August, Mr Justice Warby allowed the identities of five of Meghan’s friends, who spoke anonymously to People magazine in the US, to remain protected. He added “for the time being, at least” that should be the case.