The Duke and Duchess of Sussex’s project manager has asked a local council not to make public landscaping plans for their Frogmore Cottage home due to security reasons.

A part retrospective planning application has been submitted to the Royal Borough of Windsor and Maidenhead Council, but “national security” concerns have prompted the official to request they remain secret.

Recent royal accounts revealed £2.4 million was spent on Meghan and Harry’s grade II listed home near Windsor Castle, turning five properties back into a single residence for the couple and their baby son Archie.

Duke of Sussex moves into Frogmore Cottage
Image taken from Google Earth of Frogmore Cottage (Google Earth/PA)

The amount spent was heavily criticised by the organisation Republic, which campaigns for an elected head of state, but all fixtures and fittings for the home close to Windsor Castle were paid for privately by the duke and duchess.

A letter which appears to have been written on paper headed “Royal Household Property Section Windsor Castle” by project manager Ian Ratcliffe to a council manager responsible for enforcement and conservation has been published by the MailOnline website.

The project manager writes: “We consider that national security could be compromised if public access is given to the plans, other drawings and documents relating to this project, either in the offices of this council or on the council website where they could be viewed and copied.”

It is understood the application for external landscaping is an amendment to a previously submitted plan and the work is being funded privately.

Under planning law a retrospective planning application is needed if a change is made that requires planning permission.

If it is refused the local authority can issue an enforcement notice requiring the changes to be reversed.

King Power Royal Charity Polo Day
The Duke and Duchess of Sussex with their son Archie (Andrew Matthews/PA)

But it is likely the team carrying out the work on Harry and Meghan’s home have been keeping the local authority aware of any changes and the application is a formality.

Frogmore Cottage, which is owned by the Crown Estate, was a gift from Harry’s grandmother the Queen.

A Buckingham Palace spokeswoman said: “The letter that was submitted to the council, and the language that was used, is standard for planning applications for all royal residences. In keeping with the usual process, the details are not released for security reasons.

“This was an amendment to a planning application which was previously approved. The work was privately funded.”