Placards at the Royal Style in the Making exhibition, which opened this week, described Diana’s dress as “lent by HRH the Duke of Cambridge and HRH the Duke of Sussex”.
However, the signs will reportedly now be changed to remove Harry’s HRH style – which he agreed to stop using as part of Megxit.
A spokesman for the Royal Collection Trust said the dresses were “loaned by HRH the Duke of Cambridge and the Duke of Sussex”.
They added that “due to an administrative error, for which the Royal Collection Trust was responsible, the labels were incorrect and will be updated”.
Harry and Meghan Markle agreed to stop using their HRH styles when they quit royal duties last year.
But the couple continue to use their Duke and Duchess titles.
It comes after the Sussexes were demoted on the Royal Family’s official website.
Harry and Meghan were previously listed near the top of the page, just under Prince William and Kate.
But they have now been bumped down to below Prince Edward, Sophie, Princess Anne and Prince Andrew.
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