Future editions of the memoir will now be edited to correct the mistake, although Spencer is standing by his account of an angry telephone conversation between the pair.
A publishing source told Radar: “Changing a book after it has already gone on sale is a headache nobody wants. The text has to be corrected for future copies, and everyone involved then has to deal with the fact that an inaccurate passage appeared in the original edition.
“Piers making clear that an apology wasn’t enough and threatening legal action inevitably increased the pressure to ensure the disputed material was corrected. It is an embarrassing situation for a major memoir that was always going to receive enormous scrutiny, and a highly costly one at that.”
The photographs at the center of the dispute were published by the Sunday Mirror on November 7, 1993.
Morgan was working at The Sun at the time and did not become editor of the Daily Mirror until October 1995.
A statement issued on Spencer’s behalf said: “The photographs were published by the Sunday Mirror on November 7, 1993. Mr Morgan has pointed out that he did not join the Daily Mirror until October 1995. As an historian, accuracy is important to Earl Spencer. He therefore wishes to clarify that his assumption was incorrect. Earl Spencer apologizes to Mr Morgan for this error.”