Ms Nicholl has suggested that attempts on the part of the Duke and Duchess of Sussex to use their kingdom to the future could trigger a “prickly” response from the Royal Family.
Earlier this year, Harry and Meghan had asked for permission to continue to use their brand, Royal Sussex, once their royal careers were waiting, but the Queen rejected the suggestion.
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The royal commentator continued: “there is a feeling of anxiety on the couple will do a single activity.
“They are testing the water and everything that is a matter of cashing in on their kingdom or of the over-commercialization is going to meet a very prickly response on the part of the Palace.
“Meghan and Harry are thinking very hard about what they want to do, how they will make money.
“Public speaking is absolutely going to be one of the main ways for them to make money but I think they will be very cautious about what they speak publicly on the subject. ”
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The Queen has also accepted his grandson and his wife maintain their HRH style, but ordered them not to use their titles for commercial purposes.
Meghan and Harry have kept a low profile since their departure, but were virtually a few appearances during the lockout to express their support to charities.
Prince Harry, the last week has taken part in a message to England Rugby, to thank the supporters for their work during the pandemic, and earlier last month, he released a heartfelt video for the Invictus Games participants after the event had to be postponed.
And Meghan Markle in May delivered a commencement speech to the graduating class of his old school, Immaculate Heart High School, during which she discussed her personal experience with racism.