Prince Harry and Meghan Markle must act upon what they preach in order to earn global respect, says a royal expert.

Professor Pauline MacLaran of Royal Holloway, University of London, says the Duke and Duchess of Sussex would have appeared “hypocritical” in front of the public despite their "moving speech".

She added that the couple has a "visual opulence" that "clashes" with their message.

"[Harry's] speech was certainly moving but the problem I see with both Meghan and Harry is that they are not seen to be working for solutions to the issues they foreground i.e. poverty and environmental destruction," she noted.

"Indeed, many think they are hypocritical to be travelling frequently in private jets and sporting high-end fashion brands such as Mulberry, Manolo Blahnik, Givenchy and Cartier.

"The visual opulence of this couple seems to clash somewhat with their messages.

"For example, it would have been appropriate for Meghan to foreground sustainable fashion brands in her choice of clothing for the UN,"she noted.