The Duchess of Sussex has lost a pre-trial hearing in her case against the Mail on Sunday which has been told it can use the recent biography, Finding Freedom, as part of its defence case.
Meghan is suing the newspaper for publishing her letter which she sent to her father in the weeks after her wedding with Prince Harry.
But since the publication of the new book, which detailed Harry and Meghan's entrance and exit from the Royal Family, the newspaper's legal team requested permission to amend its written defence arguing the Sussexes had "co-operated" with the authors, Omid Scobie and Carolyn Durand.
Associated Newspapers, which owns the Mail on Sunday, claimed Meghan gave personal information to the authors "in order to set out her own version of events in a way that is favourable to her".
Last week, in the latest pre-trial hearing at the High Court, Meghan's lawyers denied there had been any collaboration and even went as far as to point out all the details the authors had got wrong in an attempt to show the did not get help with the book from the Duke and Duchess.
ITV News Royal Editor Chris Ship explains the latest development in Meghan's case against the Mail on Sunday
Judge Francesca Kaye allowed the publisher to amend its defence to rely on Finding Freedom, saying the amended defence did not raise "new defences", but simply added "further particulars" to the Mail on Sunday's case.
The judge refused a request from Meghan's barrister, Justin Rushbrook QC, to appeal against her decision.
Mr Rushbrook argued the "inherent improbability" of Meghan having co-operated with the authors of the biography was demonstrated by "simply comparing what the defendant's own articles said with what the book said about the letter" to her estranged father.
In a statement following the decision, Meghan's lawyers described it as "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."
The Duchess of Sussex is suing the newspaper for breach of privacy, copyright and data protection for publishing her "private and confidential" letter to her estranged father Thomas Markle.
She wrote the letter in August 2018, the Mail on Sunday published it in February 2019.
This was another pre-trial hearing and the full case is likely to be heard at the High Court early next year and is expected to last ten days.
Harry and Meghan have since moved to the US and stepped back from frontline royal duties.
Freedom seems to be ever more elusive for Sussexes, says Royal Editor Chris Ship
This is not the trial but yet another pre-trial hearing which will lead any casual observer of this case to conclude, correctly, it's gone on for some considerable time.
Last week, the judge told both sides they had racked up too many costs as it was revealed their combined spending on this case was in excess of £3 million.
Meghan's team insists she is not on trial, the newspaper is because it "acted unlawfully" in publishing her private letter to her father.
Her lawyers accuse the Mail on Sunday on drawing out the case to "exploit the Duchess's privacy" still further and there was no "collaboration" on the new book.
But, at this stage, it seems last month's publication of the biography "Finding Freedom" - which was supposed to show the Sussexes in a more sympathetic light - is working against Meghan.
The Mail on Sunday's owners, Associated Newspapers, has successfully persuaded a judge that their defence can be amended - even at this late stage in the legal proceedings - in order to reflect the personal nature of the biography on which the paper claims Harry and Meghan did cooperate.