Royals Prince Harry Salutes Fallen Service Members at Westminster Abbey Field of Remembrance Ceremony Prince Harry wore a somber expression for a ceremony at Westminster Abbey's Field of Remembrance to honor fallen service members ahead of Armistice Day By Stephanie Petit Stephanie Petit Stephanie Petit is a Royals Writer and Reporter at PEOPLE. People Editorial Guidelines Published on November 9, 2017 08:01 AM Share Tweet Pin Email Photo: Jeremy Selwyn - Pool/Getty The usually cheerful Prince Harry wore a somber expression for a ceremony at Westminster Abbey’s Field of Remembrance to honor fallen service members ahead of Armistice Day. The 33-year-old royal laid a Cross of Remembrance in front of wooden crosses from the Graves of Unknown British Soldiers from the First and Second World Wars and saluted. Harry, who served two tours of Afghanistan during his 10 years in the army, wore his Household Cavalry, Blues and Royals regiment dress uniform, with its dark navy frock coat. He also donned a poppy pin on his hat, a symbol that has been used since 1921 to commemorate military members who have died in war, especially poignant on Armistice Day. The poppy symbol is believed to have come from the poem “In Flanders Fields” by John McCrae, a poem about World War I. The opening stanza reads: In Flanders fields the poppies blowBetween the crosses, row on row,That mark our place; and in the skyThe larks, still bravely singing, flyScarce heard amid the guns below. Gareth Fuller/PA Images via Getty Harry’s signature smile returned as he greeted onlookers after the cross-laying ceremony. The royal was recently in Chicago to take part in the inaugural summit of the Obama Foundation, which is headed by former president Barack Obama. But local high school students were surprised by the royal’s unexpected visit with a special guest — Michelle Obama. The pair linked up to spend time with about 20 students at Hyde Park Academy, a high school across from the future site of the Obama Presidential Center on the city’s South Side — and Harry announced that he was taking full advantage of the local cuisine, including both thin and deep dish pizza. RELATED VIDEO: Prince Harry Says Troops’ Mental Wellbeing Is as Important as Being Combat Ready Later that evening, Harry spoke movingly about his late mother, Princess Diana. “I think she had a lot in common with everybody but also she certainly listened,” he said. “In a very, very short space of time she was like a vacuum going around, sucking up all the information, all the criticism, all the issues, all the positives and negatives from everybody, then putting her name and her platform toward the bigger issues that had never been talked about. “In society we suffer from this illusion, or reality, that some problems become so big that nobody wants to get involved. She was the one that changed that. I will always look up to her … everything she did and the way she did it was having an impact, making a difference,” he said.