."
The judgement found the publication of the letter also infringed Meghan's copyright but added the issue of whether she was the 'sole author' of the letter should be determined at trial.
LEGAL WIN The Duchess was suing the Mail on Sunday for privacy, copyright and data protection over five articles published in February 2019.
Mr Justice Warby said in his ruling today: "The claimant had a reasonable expectation that the contents of the Letter would remain private.
"The Mail articles interfered with that reasonable expectation."
He said "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 Mr 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."
Mr Justice Warby also found the publication of the letter infringed the duchess' copyright.
And he said the Mail on Sunday's articles "copied a large and important proportion of the work's original literary content".
But Mr Justice Warby said issues 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.
He forms part of the Palace Four - Royal aides who worked with Meghan - that could be called up to give evidence.
There will be a further hearing in March to decide "the next steps" in the legal action.
But an ANL spokesman said they were going to appeal the ruling, adding: "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."
'PAINFUL' At a hearing last month, the court was told Meghan sent the letter to her estranged dad, 76, in August 2018.
She was said to have felt forced to write the "painful" letter after they reached "breaking point".
And her lawyer Justin Rushbrooke QC described the 1,250-word letter as "a heartfelt plea from an anguished daughter to her father".
But in a sensational witness statement, Thomas Markle claimed the letter was a "criticism" of him.
He also referred to an article five anonymous friends gave to People magazine in which the letter was mentioned.
The article included a quote from a pal, saying: "After the wedding she wrote him a letter.
"She's like, 'Dad, I'm so heartbroken. I love you. I have one father. Please stop victimizing me through the media so we can repair our relationship.'"
'TOTAL LIE' But Thomas Markle branded this a "total lie" and claims the article was "expressly authorised by Meg or she had at the very least known about and approved of its publication".
Writing in his witness statement, he said: "[The People quote] suggested to people that Meg had reached out to me with the letter, saying in the letter that she loved me and that she wanted to repair our relationship.
"That suggestion was false. The letter was not an attempt at a reconciliation. It was a criticism of me.
"The letter didn't say she loved me. It did not even ask how I was. It showed no concern about the fact I had suffered a heart attack and asked no questions about my health.
"It actually signalled the end of our relationship, not a reconciliation."
Mr Markle also said the article in People magazine wrongly accused him of telling "mistruths" and "contained other inaccuracies about me".
He said: "It was wrong for People magazine to say I had lied about Meg shutting me out - she had shut me out, as the letter from her showed."
'I HAD TO DEFEND MYSELF' The dad also slammed People for suggesting he was "to blame for the end of the relationship" as he had "ignored her".
He added: "That was false. I had repeatedly tried to reach her after the wedding but I couldn't find a way of getting her to talk to me."
Thomas Markle claims he "never intended" to publicly speak out about the letter but once he saw the article, he wanted to "set the record straight".
He also said it was "important" to publish it so readers would know they were "getting the truth".
Thomas said: "The article had given an inaccurate picture of the contents of the letter and my reply and had vilified me by making out that I was dishonest, exploitative, publicity-seeking, uncaring and cold-hearted, leaving a loyal and dutiful daughter devastated.
"I had to defend myself against that attack."
In his statement, Thomas Markle also said he chose not to allow the entire letter to be published in the Mail on Sunday as it made "Meg look terrible".
He added: "I do not want to attack or hurt her."
'HEARTFELT PLEA' But lawyers for the Duchess said the publication of the "intrinsically private, personal and sensitive" letter was a "triple-barrelled invasion of her privacy rights".
Mr Rushbrooke said the letter was not "a vicious or unwarranted attack" on her dad but was instead "a message of peace".
The last line - included in court documents - read: "I ask for nothing other than peace and I wish the same for you."
The papers add: "It is a heartfelt plea from an anguished daughter to her father (the word 'pain' or 'painful' appears no fewer than five times), begging him to stop talking to the press."
Mr Rushbrooke said: "It was written, in short, by a daughter who felt she had reached a breaking point with her father."
The barrister told the court Meghan had sent it to Thomas Markle "at his home in Mexico via a trusted contact ... to reduce the risk of interception".
He described its subsequent publication as a "plain and serious invasion" of privacy.
COURT SHOWDOWN But lawyers for Associated Newspapers Limited (ANL) claim it was written "to defend her against charges of being an uncaring or unloving daughter".
Mr White said Meghan having a "fear" her letter might be intercepted showed she "must, at the very least, have appreciated that her father might choose to disclose it".
The blockbuster case - one of several brought recently by the Duke and Duchess of Sussex against media organisations - was filed by Meghan's lawyers in September 2019.
It was due to be heard at the High Court last month but was adjourned for nine months due to a "confidential" reason.
A string of pre-trial skirmishes have erupted in the build-up - including Meghan's claims ANL had an "agenda" of publishing intrusive or offensive stories about her being struck out as "irrelevant" last May.
In return, a bid to name five of Meghan's pals who gave an anonymous interview to People magazine were dismissed in August.
But in a sensational move, the MoS was given permission to rely on the unauthorised biography of Harry and Meghan, Finding Freedom by Omid Scobie and Carolyn Durand, in its defence.
ANL claimed the Duchess had "compromised" any expectation of privacy in relation to the letter by allowing details of her private life to be published in the biography.
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