Louise, the daughter of Prince Edward and Sophie, celebrates her 18th birthday in November. When she reaches the milestone, she will decide whether to style herself Her Royal Highness Princess Louise.

       Royal author Phil Dampier said there is a "strong argument" for Louise opting to use an HRH title.

       He suggested there could be a key role for her in a slimmed-down monarchy as he highlighted how the Sussexes and the Duke of York have stepped back from royal duties.

       Mr Dampier told the Telegraph: “Because she’s the granddaughter of the Queen, Lady Louise can call herself a Princess when she becomes 18 – it’s theoretically up to her.

       "And there’s a strong argument for her doing it.

       “She seems to be very mature for her age and she’s shaping up to be precisely the kind of person the Queen can rely on in the future.

       "Could there be a role for her in a slimmed-down monarchy?

       "The Queen and Philip had 1,500 patronages between them.

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       “You have to ask yourself who is going to continue their legacy with Harry and Meghan and Prince Andrew off the scene?

       "There’s a huge workload there.”

       Louise has been showered with praise following her appearance on a BBC documentary in tribute to Prince Philip, which aired on Wednesday.

       More than a dozen royals took part in Prince Philip: The Royal Family Remembers.

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       In the programme, Louise opened up on her love of carriage driving which she inherited from the Duke of Edinburgh.

       She said: “After a competition, he would always ask how it went.

       "His eyes would light up because he just gets so excited when he talks about it.”

       Louise also spoke about taking part in her grandfather's Duke of Edinburgh's Award.

       She said: “There was certainly an element of making my grandfather proud and honouring him by taking part in the award that has been so much of his life’s work."

       Louise is understood to be close to the Queen due to the Wessexes living nearby Windsor Castle.