Kate Middleton wore three poppies pinned to her black Catherine Walker outfit on Remembrance Sunday — and there’s a significant reason behind it.

The 42-year-old Princess of Wales attended two events on Nov. 9 and Nov. 10, starting with the Festival of Remembrance at Royal Albert Hall on Saturday evening, followed by Remembrance Sunday at The Cenotaph war memorial the next morning. This appearance marked an important moment in Princess Kate’s gradual return to her royal duties, following her announcement on Sept. 9 that she had finished chemotherapy, about six months after revealing her cancer diagnosis on March 22.

Standing on the Foreign Office building balcony alongside Sophie, Duchess of Edinburgh, Kate displayed three poppy pins on her coatdress. While most royal family members opted for just one, Kate’s choice to wear three was symbolic: they represent her great-grandmother’s three brothers, all of whom lost their lives in World War I, as reported by The Daily Mail.

According to The Mirror, Kate had the opportunity to view letters from her ancestors during an “emotional visit” to the Imperial War Museum in 2018. Kate began wearing three poppy pins for Remembrance Sunday as early as 2015, after having worn just one the year before, according to The Sun. She continued wearing the three-poppy set every year until 2019, when she chose to wear the Codebreakers brooch to honor her grandmother, Valerie Glassbarrow. In 2020, Kate returned to the three poppies, adding the Royal British Legion crystal flower as an accessory.

Remembrance Sunday, held on the second Sunday of November each year, is a national day of remembrance for the members of the Armed Forces in the U.K. and Commonwealth who died in conflict or war. Since joining the royal family in 2011, Kate has never missed attending Remembrance Sunday.

The poppy has been a symbol of remembrance for fallen military members since 1921. It is most commonly associated with the U.K. and Commonwealth nations for Remembrance Day on November 11, and the symbol is thought to have originated from the poem “In Flanders Fields” by John McCrae, which reflects on World War I.

The royal’s outfit on November 10 was filled with meaning, extending beyond the three poppies. She wore a coatdress by Catherine Walker, honoring her late mother-in-law, Princess Diana, who considered Walker her favorite designer and a personal friend. The night before, at the Festival of Remembrance, Kate also paid homage to Diana with her choice of Collingwood pearl earrings.

On November 10, during Remembrance Sunday, Kate wore a pair of Bahrain Pearl Drop earrings, which were a gift from Queen Elizabeth. The Queen had received the earrings as a wedding gift when she married Prince Philip on November 20, 1947. (The Princess of Wales had previously worn these significant earrings at the late Queen’s funeral in September 2022.)

Like Kate, Queen Elizabeth also chose to wear multiple poppies. The late monarch wore five poppies, representing the Royal Navy, the Royal Marines, the British Army, the Royal Air Force, and the Defense Medical Services.

Other working royals who attended The Cenotaph alongside Kate and Sophie included King Charles, Prince William, Prince Edward, Princess Anne, Vice Admiral Sir Timothy Laurence, Prince Richard, the Duke of Gloucester, Birgitte, the Duchess of Gloucester, and Prince Edward, the Duke of Kent.

Queen Camilla was absent from this weekend’s Remembrance events, missing both on November 9 and November 10 as she continues to recover from a chest infection. On November 9, the palace issued a statement confirming her absence, which said, “Following doctors’ guidance to ensure a full recovery from a seasonal chest infection, and to protect others from any potential risk, Her Majesty will not attend this weekend’s Remembrance events.”

“While this is a source of great disappointment to The Queen, she will mark the occasion privately at home and hopes to return to public duties early next week,” the statement added.

This weekend marked a significant milestone in Princess Kate’s gradual return to public duties, which is expected to continue in December with her annual Christmas carol concert at Westminster Abbey. In her emotional video from September 9, where she announced she had finished chemotherapy, she shared, “Doing what I can to stay cancer free is now my focus. Although I have finished chemotherapy, my path to healing and full recovery is long and I must continue to take each day as it comes.”

She also mentioned, “I am, however, looking forward to being back at work and undertaking a few more public engagements in the coming months when I can.” She has stayed true to her promise, attending both private and photographed meetings at Windsor Castle for some of her important causes, and also appeared with the Prince of Wales in Southport, England, on October 10 ahead of her Remembrance duties over the weekend.

“She is undoubtedly a crucial member of the royal family, significant both symbolically and in reality as a future Queen,” royal biographer Sally Bedell Smith tells PEOPLE. “It was beneficial for people to see her. You can’t say she is back … but she is coming back.”

“Being a senior member of the royal family and participating in these ceremonial events is clearly important to her,” Bedell Smith adds.