The Duchess of Sussex has criticised the publisher of The Mail On Sunday for “blatantly exploiting” her privacy after winning her High Court claim against the newspaper for misuse of private information.

Meghan, 39, sued Associated Newspapers Limited (ANL), the publisher of The Mail On Sunday and MailOnline, over a series of February 2019 articles which reproduced parts of a “personal and private” handwritten letter sent to her estranged father, 76-year-old Thomas Markle.

She took legal action for alleged misuse of private information, copyright infringement and breach of the Data Protection Act over five articles which included extracts from the letter sent in August 2018.

At a hearing in January, the duchess’ lawyers applied for “summary judgment” in relation to her privacy and copyright claims, a legal step which would see those parts of the case resolved without a trial, arguing that ANL had “no prospect” of defending them.

In a ruling on Thursday, Mr Justice Warby granted Meghan summary judgment in relation to her privacy claim, ruling that the publication of her letter to her father was “manifestly excessive and hence unlawful”.

The judge 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.”

Mr Justice Warby said that “the only tenable justification for any such interference was to correct some inaccuracies about the letter”, contained in an article in People magazine which featured an interview with five friends of Meghan.

But the judge 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.”

Mr Justice Warby also granted summary judgment in relation to most of the duchess’ copyright claim, saying The Mail On Sunday’s articles “copied a large and important proportion of the work’s original literary content”.

The judge said ANL’s case on ownership of the copyright of the letter “seem to me to occupy the shadowland between improbability and unreality”, adding: “There is no room for doubt that the defendant’s conduct involved an infringement of copyright in the electronic draft (of the letter) of which the claimant was the owner or, at worst, a co-owner.”

However, he said the issue of whether Meghan was “the sole author”, or whether Jason Knauf, formerly communications secretary to the Duke and Duchess of Sussex, was a “co-author”, should be determined at a trial, despite being one “of minor significance in the overall context”.

Mr Justice Warby also said that there would be a further hearing on March 2 to decide “the next steps” in the legal action.

Meghan’s data protection claim was not considered at the hearing in January and is still outstanding.

In a statement after the ruling, the duchess said: “After two long years of pursuing litigation, I am grateful to the courts for holding Associated Newspapers and The Mail On Sunday to account for their illegal and dehumanising practices.”

She added: “The world needs reliable, fact-checked, high-quality news.

“What The Mail On Sunday and its partner publications do is the opposite.

“We all lose when misinformation sells more than truth, when moral exploitation sells more than decency, and when companies create their business model to profit from people’s pain.

“But, for today, with this comprehensive win on both privacy and copyright, we have all won.

“We now know, and hope it creates legal precedent, that you cannot take somebody’s privacy and exploit it in a privacy case, as the defendant has blatantly done over the past two years.”

A spokesperson for ANL said: “We are very surprised by today’s summary judgment and disappointed at being denied the chance to have all the evidence heard and tested in open court at a full trial.

“We are carefully considering the judgment’s contents and will decide in due course whether to lodge an appeal.”

At the hearing in January, the High Court heard how the duchess sent the “heartfelt” five-page letter to her father’s home in Mexico “via a trusted contact” in August 2018 in order to “minimise the risk of interception”.

Meghan’s lawyers said the publication of the letter was “self-evidently… highly intrusive”, describing it as “a triple-barrelled invasion of her privacy rights”.

But ANL claimed Meghan wrote the letter “with a view to it being disclosed publicly at some future point” in order to “defend her against charges of being an uncaring or unloving daughter”.

In a witness statement, Mr Markle claimed he “still believes” his daughter wanted “her account” of the letter to be made public, saying the People magazine interview “had either been expressly authorised by Meg or she had at the very least known about and approved of its publication”.

Meghan’s father said he “had never intended to talk publicly about Meg’s letter to me”, but he felt the People article “vilified me by making out that I was dishonest, exploitative, publicity-seeking, uncaring and cold-hearted, leaving a loyal and dutiful daughter devastated”.

Mr Markle added: “I had to defend myself against that attack.”

The court also received a letter from four former employees of the Duke and Duchess of Sussex, the so-called “Palace Four”, who said they may have evidence which could “shed some light” on the letter, but that they did not “wish to take sides in the dispute”.

The letter was sent on behalf of Mr Knauf as well as Christian Jones, their former deputy communications secretary, Samantha Cohen, formerly the Sussexes’ private secretary, and Sara Latham, their former director of communications.

Mr Justice Warby also received a letter from one of the authors of an unauthorised biography of the Duke and Duchess of Sussex, who denied seeing any part of the letter before it was published by The Mail On Sunday.

Omid Scobie, who wrote Finding Freedom with co-author Carolyn Durand, “angrily denied” ANL’s claim that he received a copy of the letter before publication of the book, the judge said.

Meghan’s victory against ANL comes less than two weeks after Harry accepted an apology and “substantial damages” from the publisher over “baseless, false and defamatory” allegations he snubbed the Royal Marines after stepping down as a senior royal.