Eight of Queen Elizabeth II’s grandchildren will stand vigil beside her coffin in Westminster Hall for 15 minutes on Saturday night.
Prince William will stand at the head, with Harry at the foot.
At the King’s request, both the Prince of Wales and the Duchess of Sussex be in military uniform.
The other grandchildren will be in morning suits and dark formal dresses with decorations.
William will be flanked by his cousins Zara Tindall and Peter Philips, Princess Anne's children.
Prince Harry and King Charles III
PA
King Charles III leading members of the Royal Family in mourning
POOL
While Harry will be with Prince Andrew's daughters, Princesses Beatrice and Eugenie.
Prince Edward's children, Lady Louise Windsor and James, Viscount Severn, will stand near the middle of their grandmother’s coffin.
The grandchildren are said to be very keen to pay their respects – just as their parents are doing on Friday evening.
Despite seeing front-line action during two tours of duty in Afghanistan, Harry has so far been denied the chance to wear his military uniform.
This is because he is no longer a working royal – and he has so far worn a morning suit on public occasions of mourning Queen Elizabeth II.
The former Army officer has been seen wearing civilian dress for official events, such as when he walked behind his grandmother’s coffin on Wednesday.
An exception had been made for Prince Andrew, who is no longer a working royal but will wear his military uniform as a “special mark of respect” for his mother.
The Duke of York will stand guard around her coffin during a vigil with his siblings on Friday evening.