The palace said last week that the two would no longer use their royal titles – His and His Royal Highness – as of this spring, but would be called "Harry, Duke of Sussex" and "Meghan, Duchess of Sussex".
The problem is that this format was adopted by Sarah Ferguson – now called "Sarah, Duchess of York" – after she divorced Prince Andrew in 1996. And Harry's mother became known as Diana, Princess of Wales, after the Prince Charles's divorce.
According to the palace, the titles of Duke and Duchess of Sussex are not subject to change, but updated guidelines are being prepared on how names should be formatted.
Buckingham Palace said its earlier guidance on the royal couple's title was erroneous, and is now in conference with the Garter King of Arms – specialist in title and protocol issues – to issue updated guidance.
Meghan received the title of Her Royal Highness, the Duchess of Sussex, when she married Prince Harry in May 2018.
Harry's full title was His Royal Highness, the Duke of Sussex, Earl of Dumbarton and Baron Kilkeel.