When Prince Harry and Meghan stepped down as working royals there was an agreement to stop using HRH, which stands for Her/His Royal Highness, but they still hold the titles. Sources close to the California-based couple reject that this card was a breach of the agreement struck on their departure from royal duties.

Meghan has defied a deal with the late queen to continue using her HRH title. King Charles is turning a blind eye. King William won’t.

Since it emerged that Meghan Markle sent a gift basket to a friend with a card that described her as 'HRH The Duchess of Sussex' controversy has grown - now a constitutional expert has weighed in