LONDON -- The publisher of Britain's Mail on Sunday newspaper can use the contents of a recent behind-the scenes book about the Duke and Duchess of Sussex in its legal defence for an invasion of privacy lawsuit brought by the duchess, a judge ruled Tuesday.

Judge Francesca Kaye gave Associated Newspapers Ltd. permission to amend its defence to add “further particulars” relating to the book published last month, “Finding Freedom.”

The former Meghan Markle, 39, is suing the publisher over five February 2019 articles in the Mail on Sunday and on the MailOnline website that published portions of a handwritten letter she wrote to her estranged father, Thomas Markle, after her marriage to Harry in 2018.

Associated Newspapers is contesting the claim. Its lawyers argue that Meghan made personal information public by co-operating with the authors of the book “in order to set out her own version of events in a way that is favourable to her.”

Antony White, a lawyer for Associated Newspapers, said in written court submissions that the book appeared to have been written with Meghan and Harry's “extensive co-operation.”

Meghan's lawyers deny that she collaborated with the book's authors, Carolyn Durand and Omid Scobie.

American actress Meghan Markle, star of TV legal drama “Suits,” married Harry, one of the grandsons of Queen Elizabeth II, in a lavish ceremony at Windsor Castle in May 2018. Their son, Archie, was born the following year.

Early this year, the couple announced they were quitting royal duties and moving to North America, citing what they said was the unbearable intrusions and racist attitudes of the British media. They recently bought a house in Santa Barbara, California.

A full hearing in her lawsuit against Associated Newspapers is due to start in January.