Charles instructed the Lord Chamberlain to contact government departments and the military following requests for guidance after the couple returned to the UK to begin a new life last month.

The Sussexes stepped down as working royals in 2020 but returned to the UK on August 26, with rumours rife as to the reason behind the unexpected development.

The message emphasises that the position agreed in 2020 when the Sussexes left the UK - the so-called Sandringham Agreement - is still in place.

In a letter the Lord Chamberlain, the most senior officer of the Royal Household, stated: “Following the decision by the Duke and Duchess of Sussex to relocate to the UK, we have received a number of requests for guidance. To help avoid doubt or confusion, The King has directed that the following information be shared.

“It is well known that in January 2020 the Duke and Duchess stepped down from undertaking representative duties on behalf of The Sovereign, and are no longer working Members of The Royal Family.

“This position, distinct from the State and Royal duties undertaken by the working Royal Family, and with the personal latitude it brings the couple in respect of financial independence and protection of their privacy as they would wish, will continue to be fully respected.”

On Monday a picture emerged of Prince Harry at Tower Bridge Studios, where Diary of a CEO and BBC’s The Apprentice is filmed.

The studio posted two pictures to their Instagram after he signed their wall. The pictures were captioned: “Thank you Prince Harry for choosing Tower Bridge Studios! It was an absolute pleasure to have you in our studios and signing our wall. We look forward to welcoming your back again. “

Harry and Meghan had been living in Montecito, California for years before their return, with Harry saying last year that he “can’t see a world in which I would bring my wife and children back to the UK” after losing their case for state-funded security.

The news of the family’s return to the UK was therefore met with utter surprise; no official reason has been given, but many have speculated that Harry may want to be back for his father, King Charles, amid the monarch’s ongoing treatment for cancer.

It has been reported that King Charles was only made aware that his youngest child is returning with his family days before the news leaked to the public.

It is believed the family have set up in the Cotswolds, with school parents in the region reportedly receiving letters of guidance about their children’s potential royal classmates.

That the Sussexes would relocate to the Cotswolds makes sense, as the area speaks to both Harry’s history and Meghan’s Hollywood connections.

In recent areas, the area, which covers five counties in the south-west of England, has become home to a host of high-profile stars, from the Beckhams to Ellen Degeneres.

Harry also spent much of his childhood around Gloucestershire, Oxfordshire and Wiltshire, including at his father’s private residence, Highgrove, in Tetbury.

Former actress Meghan, meanwhile, is said to be “in talks” for a role in season three of Guy Ritchie’s Netflix series The Gentlemen.