Meghan Markle shared a message on Instagram that addressed herself and or Prince Harry with the title "Your Royal Highness", despite the term being banned after they quit as senior working royals in 2020. Meghan and Harry never formally surrendered their His and Her Royal Highness (HRH) titles but agreed to stop using them after they quit the Royal Family and left the United Kingdom.

The Duchess of Sussex published a letter from Ukraine's vice president this weekend that began, "Your Royal Highness, I would like to express my sincere thanks for everything your family is doing for Ukraine."

Since posting, this has created growing calls in the UK for the couple to be stripped of their titles, reports The Daily Beast. A friend of King Charles said: "It’s outrageous. Every time you think they can’t make it worse, they make it worse.

"The deal with the HRH was a way to stop them cashing in while letting them walk away with pride and dignity and trust, and now Markle is using her HRH on a website which seems to exist to sell jam."

The source also added that the King "doesn't allow himself to get angry about things like this anymore".

A friend of Prince William’s also told The Daily Beast: "It’s actually quite a clever way of testing the water, because there is deniability there, she can say, 'Well, I just wanted to publish this nice letter to raise awareness for Ukraine, and oops! they got my name wrong—but oh, actually, now I think of it, I never gave the title up anyway, and maybe I will start using it again.'"

They added: "It’s a step in the wrong direction, basically, away from the agreement. You’d have to be an idiot to believe that she didn’t know exactly what she was doing when she posted that message, unedited, to her stories."

Part of the statement released by Buckingham Palace after Harry and Meghan decided to step down read: "The Sussexes will not use their HRH titles as they are no longer working members of the Royal Family."

Last weekend, the Duke of Sussex met war victims in Ukraine in an unannounced visit to the country as part of his work with wounded veterans.

Prince Harry visited the Superhumans Centre, an orthopaedic clinic in Lviv that treats and rehabilitates wounded military personnel and civilians.

Harry, who served 10 years in the British Army, including two tours in Afghanistan, has made helping injured soldiers one of his most prominent causes.

On his return, Meghan shared images of the special edible gifts Harry had brought home from his travels in her Instagram Stories.