The Duchess of Sussex’s letter to her estranged father Thomas Markle was “written with public consumption in mind as a possibility”, the Court of Appeal has heard.

Lawyers for the Mail On Sunday’s publisher told senior judges they want to rely on new evidence from Jason Knauf – former communications secretary to the Duke and Duchess of Sussex – which suggests Meghan suspected her father may disclose the letter to the media.

The newspaper’s publisher, Associated Newspapers Limited (ANL), began its appeal on Tuesday against a High Court judge’s decision that the publication of the letter was “unlawful”.

Meghan, 40, sued ANL, which is also the publisher of MailOnline, over a series of articles which reproduced parts of a “personal and private” letter to Mr Markle, 77, in August 2018.

She claimed the five articles, published in print and online in February 2019, misused her private information, infringed her copyright and breached the Data Protection Act.

Meghan won her case earlier this year after Lord Justice Warby ruled that ANL’s publication of Meghan’s letter to her father was “manifestly excessive and hence unlawful” in a summary judgment – avoiding the need for a trial.

However, at the outset of ANL’s challenge, due to be heard over three days, Andrew Caldecott QC, representing the publisher, said Mr Knauf’s evidence casts doubt on the basis of the judge’s ruling.

He told the court: “We read the judgment as implicitly accepting that the letter was crafted as an intimate communication for her father’s eyes only.

“The fundamental point turns out to be false on the new evidence. The letter was crafted specifically with the potential of public consumption in mind because the claimant appreciated Mr Markle might disclose it to the media.”

Mr Caldecott added that Meghan “made no effort to correct” an article in People magazine in the US, which featured an interview with five friends of the Duchess of Sussex, adding that Mr Markle had “considered the article to be a serious attack on him”.

The barrister also said ANL’s defence to Meghan’s privacy claim was arguable and should have gone to a trial.

He told the court her claim was “diminished and outweighed” by her father’s right to reply following “false or misleading” allegations published in People magazine in the US.

He said: “The claimant’s letter and the People article both make allegations against Mr Markle of cruelly cold-shouldering the claimant in the pre-wedding period… The article, or its gist, was reported worldwide.”

The barrister added: “We say there was a difference between what Mr Markle said and what he was presented as saying.”

He concluded: “The defendant submits it has a strongly arguable case that, by the time of the publication of the articles, the claimant no longer had a reasonable expectation of privacy of the text of the letter.”

Meghan’s legal team are opposing the appeal and argue that the judge reached the right conclusions on the evidence before him.

They also object to the introduction of Mr Knauf’s new evidence and say that, if the court accepts his statement, Meghan will also wish to put forward new evidence.

Giving a ruling in February, Lord Justice Warby said: “It was, in short, a personal and private letter.

“The majority of what was published was about the claimant’s own behaviour, her feelings of anguish about her father’s behaviour, as she saw it, and the resulting rift between them.

“These are inherently private and personal matters.”

The judge said “the only tenable justification for any such interference was to correct some inaccuracies about the letter”, contained in an article in People magazine, published days before ANL’s five articles, which featured an interview with five friends of Meghan.

But Lord Justice Warby added: “The inescapable conclusion is that, save to the very limited extent I have identified, the disclosures made were not a necessary or proportionate means of serving that purpose.

“For the most part they did not serve that purpose at all.

“Taken as a whole, the disclosures were manifestly excessive and hence unlawful.”

In March, the publisher was ordered to print a statement on the front page of the Mail On Sunday and a notice on page three of the paper stating it “infringed her copyright” by publishing parts of the letter to Mr Markle.

But the front-page statement about Meghan’s victory has not been published yet as it is on hold pending the outcome of the appeal.

In a further ruling on copyright issues in May, the judge said ANL must “use its best endeavours” to locate any copies of the draft of Meghan’s letter to Mr Markle and provide them to the publisher’s lawyers, who will destroy them “at the end of the action, so long as the claimant ultimately succeeds”.

The judge concluded he could make the rulings without the need for a full trial of the issues involved.

The publisher’s appeal is being heard by Sir Geoffrey Vos, Dame Victoria Sharp and Lord Justice Bean over three days, and the judges are expected to give their ruling at a later date.

Meghan was asked about the appeal at the New York Times DealBook online summit on Tuesday, and said: “In terms of the appeal, I won the case, and this issue, frankly, has been going on when I had no children at all… I now have two children, as you know.

“So it’s an arduous process, but again it’s just me standing up for what’s right, which I think is important across the board, be it in this case or in the other things we’ve been talking about today.

“At a certain point, no matter how difficult it is, you know the difference between right and wrong, you must stand up for what’s right and that’s what I’m doing.”