Last year, High Court judge Sir Peter Lane ruled that Ravec's decision, taken in early 2020 after the Duke and Duchess of Sussex quit as senior working royals, was not irrational or procedurally unfair.

The Home Office, which has legal responsibility for Ravec's decisions, is opposing the appeal, with its lawyers previously telling the High Court that decisions were taken on a "case-by-case" basis.

During today's hearing, Shaheed Fatima KC, for the Duke of Sussex, said in a written submission to the Court of Appeal: "This appeal concerns the most fundamental right: to safety and security of person.

"On January 8 2020, (the Duke of Sussex) and his wife felt forced to step back from the role of full-time official working members of the royal family as they considered they were not being protected by the institution, but they wished to continue their duties in support of the late Queen as privately funded members of the royal family."

Ms Fatima later said that Harry was "not in a position to make any informed representations to Ravec".

She added: (His) security does not appear to have been discussed at any formal Ravec meeting and there are no official notes or detailed minutes recording the approach to be taken to (his) security and the rationale for it."

Elsewhere, she said that Ravec did not get an assessment from an "expert specialist body called the risk management board, or the RMB" and came up with a "different and so-called 'bespoke process"'.

She said: "The appellant does not accept that 'bespoke' means 'better'. In fact, in his submission, it means that he has been singled out for different, unjustified and inferior treatment.

"Not only does this bespoke process not involve the RMB, it also involves Ravec considering the reason why the appellant is attending a particular event, even though that is plainly irrelevant to the question of security."

The Duke of Sussex waved at reporters as he entered the Royal Courts of Justice this morning.

He was wearing a dark suit with a blue patterned tie.

The prince stayed silent when a reporter asked him: "Did you speak to your dad?"