So something I've just been reminded of is that Meghan allegedly leaked some court documents during her libel case against the Mail via OS. And the judge said that there is no other way OS could have got the docs. Citation is from the Sun, but it's just reporting what the judge said rather than opinion:
Mr Justice Warby today ruled the identities of Meghan’s friends must remain confidential “in the interests of justice” – saying the decision had been made “for the time being”.
However, in a judgment released today, he said there was evidence that Meghan's side had "briefed the press" about the initial application to stop her friends from being publicly named during the High Court case.
Mr Justice Warby said reporter Mr Scobie - who is set to release a biography about the couple next week - tweeted about the application just 58 minutes after they were filed.
In the 20-page document, Mr Justice Warby said the application to stop the naming of Meghan's five friends was filed at 8.32am, with Mr Scobie tweeting the file's cover page at 9.30am on July 9.
The tweet said: "Lawyers for Duchess Meghan have filed a court order to stop the Mail from printing the names of five confidential potential witnesses.
"A close source says, '[This] is only being done so the Mail can target five innocent women through the pages of its newspapers and its website'."
Mr Justice Warby said in his judgment: "The inference invited is that he had been provided with a copy by representatives of the claimant.
"This seems very likely."
I'm not sure why anyone thinks MM is not the main source material for Endgame.