The Queen's eight grandchildren held a 15-minute vigil around her coffin - with Prince Harry wearing military uniform at the King's request.
Prince William was at the head of the coffin as the Duke of Sussex stood at the foot.
It was the first time Harry, who served on the front line during two tours of duty in Afghanistan, has been seen wearing military uniform while publicly mourning his grandmother.
The Duke of Sussex lost the automatic right to do so when he stepped back as a working royal in 2020.
However, Buckingham Palace confirmed both Prince William and Prince Harry would wear military uniform at the "King's request".
William wore the Blues and Royals No 1 uniform, the Garter Sash, the Garter Star, the Golden, Diamond and Platinum Jubilee Medals and RAF pilot wings.
The other six grandchildren wore morning coats and dark formal dress with decorations.
Prince William was flanked by Zara Tindall and Peter Phillips, the children of Princess Anne.
Prince Harry was flanked by Princesses Beatrice and Eugenie, the daughters of Prince Andrew.
Lady Louise and Viscount Severn, the children of Prince Edward, were at the middle of the coffin in Westminster Hall.
On Friday evening, the Queen's children - Charles, the Duke of York, the Princess Royal and the Earl of Wessex - held their own vigil around the coffin.
Prince Andrew was seen in uniform for the first time in recent days after being given special dispensation to wear it.
He stopped being a working royal, and lost the automatic right to wear military dress, after details emerged of his relationship with the billionaire paedophile Jeffery Epstein.
The Queen's grandchildren held their vigil as final preparations are under way for the funeral on Monday, with politicians and royal dignitaries from around the world expected to arrive throughout the weekend.
Thousands of people are continuing to queue to see the Queen's coffin lying in state ahead of the service, with some facing more than a day in line.
Meanwhile, King Charles visited the Metropolitan Police headquarters on Saturday to thank the emergency services for their support in organising his mother's funeral.
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It came as Prince Edward and his wife Sophie, the Countess of Wessex, walked out of the gates of Buckingham Palace on Saturday to greet crowds.
Sophie was handed bouquets of flowers and a teddy by well-wishers outside.
US President Joe Biden and the First Lady are heading to London on Saturday ahead of the Queen's funeral.
Mr Biden and his wife Jill will pay their respects to the late sovereign on Sunday as her coffin lies in Westminster Hall.