The King today made it clear that the Duke and Duchess of Sussex are to remain as private citizens who will not undertake royal duties despite their return to the UK.

In a letter of guidance to 'senior stakeholders' in the government, military and those who represent the Royal Family around the country, Charles said Harry and Meghan's titles are in abeyance and they should not be treated as working royals.

The monarch has also advised that 'security issues should continue to be directed to the relevant police authorities'. 

The guidance was sent out under the King's instructions by his most senior official, the Lord Chamberlain.

Royal officials have made clear it is sent in 'full accordance' with the Sussex family's stated wishes to remain private citizens while in the UK, and in keeping with what became known as 'the Sandringham agreement' – 'which still stands'.

The letter, which confirms Harry and Meghan cannot use their HRH titles, has been shared with the Duke and Duchess. 

It came on the same day that Harry was pictured in Britain for the first time since he and Meghan returned a fortnight ago. 

The Duke smiled broadly while visiting Tower Bridge Studios - the central London premises where Diary of a CEO and The Apprentice are filmed - hours after the King's letter was released. 

The studio's Instagram page posted: '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 you back again.'

Charles' letter read: '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.'

The letter – which was sent to relevant senior stakeholders across Government, the military and Lord Lieutenancies by the Lord Benyon, the Lord Chamberlain, who represents the Royal Household – continues: 'It follows that there is no change to the current status of the Duke and Duchess of Sussex. Their styles as His and Her Royal Highness remain in abeyance and are not used. 

'The charitable work of the Duke and Duchess is a personal matter for them both and undertaken in their private capacity. In short, their position is akin to private citizens with commercial and charitable interests. 

'Any specific questions from official and State organisations about the courtesies which should be extended to the Duke and Duchess, and particularly where recourse to public funds may be required, should be directed to Buckingham Palace. Any operational security issues should continue to be directed to the relevant police authorities.

'All correspondence and administrative questions relating to the couple should be sent directly to their office, which will continue to operate separately from the Royal Household.'

Officials have insisted there is nothing controversial or new around the letter's contents, which simply make clear 'the continued position for the benefit of all parties'.

However, the fact that the Palace needed to send the letter out in the first place demonstrates the level of confusion and consternation Harry and Meghan's sudden to return to the UK has caused.

It will also be seen by some as a determined effort to put the couple in their place after sources close to them have repeatedly briefed out to favoured media in recent weeks their plans to undertake more charitable duties back in the UK.

The Sussexes returned to Britain a fortnight ago with their two children for what has been described as an 'extended' stay. Prince Archie and Princess Lilibet are believed to be starting at a British school this week. 

The wider issue of a framework for security provision remains for the Executive Committee for the Protection of Royalty and Public Figures (Ravec) to determine, a source stressed.

Officials could not be pinned down as to how many people the letter had been sent to, particularly in government, aside from saying 'a select few at an appropriate grade of seniority'. 

Lord Lieutenants act as the personal representative of the monarch on in their assigned county or area. There are currently 98 across the UK.