All eight of Elizabeth’s grandchildren, including King Charles’ sons, Prince William and Prince Harry, stood vigil for 15 minutes at Westminster Hall, where the queen lies in state.
Harry, Duke of Sussex, stood at the foot with Prince Andrew's daughters, Princess Beatrice and Princess Eugenie, flanking him. Meanwhile the children of Prince Edward, Lady Louise and James, Viscount Severn, each stood to the sides of the coffin.
When the vigil was completed, the grandchildren filed out of the hall behind William, moving in perfect synchronization.
NBC News royal contributor Suzannah Lipscomb noted that this was the first time the grandchildren have done a vigil like this.
"It is a real honor that they are giving to their grandmother," she said.
At the request of the king, both William and Harry wore their military uniforms to the solemn event — which marks a change from prior funeral plans.
As a nonworking royal, Harry, like Andrew, won’t be wearing his uniform at the funeral. In fact, he wasn’t expected to wear his uniform at all, as a spokesperson for the prince announced earlier this week, until the king's request.
"(Harry has) been asked by the king to wear (his) uniform as a mark of respect for the queen," Lipscomb said. "The uniform is conveying honor on the monarch (he is) revering and whose vigil (he is) carrying out, as opposed to the wearer."
The queen's other grandchildren wore morning coats and dark formal dress for the vigil.
None of their spouses joined them, though both William and Harry had their wives, the former Kate Middleton and Meghan Markle, by their sides last weekend, when they greeted mourners outside the gates of Windsor Castle.
The Sept. 17 vigil took place after the queen's children stood vigil at the sides of her catafalque twice this week.
On Sept. 12, Charles was joined by his brothers, Andrew and Edward, and his sister, Anne, at the Vigil of the Princes at St. Giles' Cathedral in Edinburgh, Scotland. Anne's presence marked the first time a female member of the British royal family participated in such an event.
On Sept. 16, the queen's children assembled for another Vigil of Princes held at the Palace of Westminster.
The location is where Britain’s Houses of Parliament meet — both the House of Commons and the House of Lords — and, as such, the 19th century building has played an important role in the nation’s history.
In 2012, the queen noted of Westminster Hall, “We are reminded here of our past, of the continuity of our national story and the virtues of resilience, ingenuity and tolerance which created it.”
Of course, the royals aren’t the only ones who’ve gathered at Westminster Hall to honor the queen.
On Sept. 16, TODAY’s senior international correspondent Keir Simmons revealed that the line of public mourners waiting outside Westminster Hall stretched “along the famous river Thames and three miles across London” as Britons waited “for just a few last minutes with their late queen.” Related: