It was believed to be the first time a judge had demanded such a declaration and was described by media lawyers as “extraordinary” and “troubling.”
The Duchess, 39, sued Associated Newspapers over the publication of five articles that reproduced extracts of the five-page handwritten letter.
She was last month granted a summary judgment, a legal step that saw the privacy claim and the bulk of the copyright claim resolved in her favour without trial.
The Duchess’s lawyers sought an order requiring Associated to publish a statement about the copyright win on the front page of the Mail On Sunday and the home page of MailOnline “to act as a deterrent to future infringers”.
Lord Justice Warby agreed, ruling that the newspaper must carry a statement that gave similar prominence to the original story.
He ordered that an 86-word notice must also be printed “above the fold” on page three stating that it had “infringed her copyright” by publishing parts of the letter.
The judge accepted that such an order represented an “interference with freedom of expression” that needed legal justification but said the “plain and obvious” aim was to protect and vindicate the Duchess’s civil rights.
Associated argued that rather than publishing the statement in the same size font as the original headline, it should be allowed to run it along the bottom of the page as a sub-banner in a smaller font, due to the number of words.
It said the Duchess’s proposals “would represent a disproportionate amount of the front page and a vastly disproportionate interference” with its freedom of expression rights.
Meghan’s riposte, the judge noted, was that this was a problem of its own making.