Harry and Meghan built a website based on the title which started from their Instagram page. They have also registered Sussex Royal as a trademark internationally on items including clothing, stationery, books and teaching materials.

However, the Queen and other senior officials have said they should no longer be using the term ‘royal’ their merchandising. A royal source said the future use of the term by Harry and Meghan ‘needed to be reviewed’ and that discussions were ongoing.

The source said: ‘As the Duke and Duchess of Sussex are stepping back as senior members of the royal family and will work towards financial independence, use of the word “royal”, in this context, needed to be reviewed.

‘As part of the process to transition the Duke and Duchess of Sussex into their new chapter, planning has been well underway around the launch of their new non-profit organisation.’

The Sussexes are living in Canada with their baby son Archie Mountbatten-Windsor as they prepare to drop their HRH styles and quit the monarchy.

Buckingham Palace said their new life away from royal duties would begin in the spring of this year.

Harry and Meghan first used the Sussex Royal name when they created their own household, following a split from the Duke and Duchess of Cambridge and Kensington Palace.

However, they may now have to re-name their website and start from scratch with their re-branding.

Meanwhile, the National Theatre’s artistic director has dismissed claims of a rift with its patron, the Duchess of Sussex.

The Daily Mail had reported that ‘National Theatre bosses were left fuming’ when the former actress, who became the venue’s patron in January 2019, and her husband the Duke of Sussex announced they were scaling back their royal duties and moving to Canada.

But Rufus Norris said the report was incorrect.

‘A complete fiction,’ he told The Daily Telegraph.

‘From our perspective, I don’t think it’s going to change anything.’

The theatre has become known in recent times for its community theatre programmes as much as for hosting performances from Ralph Fiennes and Cate Blanchett.

It will have achieved Mr Norris’s five-year targets of 50% of its writers, directors and actors being female as well as 20% of writers and directors and 25% of performers being ‘people of colour’ by next year, the artistic director said.

Mr Norris also said he was looking forward to the Prime Minister Boris Johnson’s forthcoming biography of William Shakespeare.

‘Here is someone who understands that the most famous Briton that ever walked was a playwright,’ he said.