Kate Middleton Appears to Fight Back Tears in Emotional Moment at Remembrance Event

The Princess of Wales appeared emotional at the solemn service

Kate Middleton let her emotions show during the Festival of Remembrance, her first major engagement with the royal family since completing chemotherapy.

On Nov. 9, the Princess of Wales, 42, joined Prince William, King Charles, Princess Anne and other working members of the royal family for the solemn event at Royal Albert Hall in London to honor the service and sacrifices of military personnel.

Princess Kate appeared to fight back tears during a standing ovation for World War II troops, as captured in footage shared by The Sun. Later in the evening service, the Princess of Wales appeared visibly emotional, seemingly holding her breath in a poignant moment.

For Kate, the evening represented an emotional return to public life after months away, following a "brutal" year, as described by William, amid her own and King Charles’ cancer diagnoses and treatment.

"She is clearly a vital piece of the royal family, a really important both symbolically and in reality as a future Queen," royal biographer Sally Bedell Smith tells PEOPLE. "It was good that people saw her. You can’t say she is back...but she is coming back,"

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The family's appearance at the festival was especially momentous this year, as it marked Princess Kate's first major event after she announced on Sept. 9 that she completed chemotherapy treatment. The Princess of Wales shared in March that she was undergoing treatment for cancer, and subsequently stepped outside of the limelight for much of the year to focus on her health.

In a rare display of PDA, Prince William protectively put an arm around his wife's back several times as they made their way into Royal Albert Hall on Nov. 9.

Bedell Smith tells PEOPLE that the touching gesture harkens back to what the Prince of Wales said last week about 2024 being the "hardest year of his life" amid the cancer diagnoses of Princess Kate and his father the King, and a deep desire to protect his wife.

"He was putting his arm around her and being very protective. It is connected to what he said about this being a ‘brutal’ year," Bedell Smith tells PEOPLE. "I guess you can only imagine that he had witnessed a pretty arduous situation for her, through this year."

Related: Prince William Says Kate Middleton Will 'Hopefully' Join Him on Royal Trips Next Year amid Cancer Recovery

"He is not known for expressing his emotions in that way. It was solicitous and protective in a very understandable way. There was a reason behind it, she was going into a big event where she was going to be on display," Bedell Smith adds. "There was an element of reassurance in the way he was behaving."

It's tradition for the British royals to attend the Festival of Remembrance as a show of support in the run-up to Remembrance Sunday, which honors the wartime sacrifices of British and Commonwealth Armed Forces personnel. This year's event showcased the contributions of the World II generation during the 80th anniversary of the D-Day Landings.

Following the Festival of Remembrance, Princess Kate made her first consecutive royal appearance by stepping out at the Cenotaph Service on Remembrance Sunday. She appeared on the balcony of a government building above the war memorial during the service on Nov. 10, and watched on as King Charles and Prince William laid wreaths.

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Though her attendance at the Remembrance events (the Festival of Remembrance on Saturday, and Remembrance Sunday at the Cenotaph) is not to be interpreted as a full return to royal duties, fans were reassured to see the Princess of Wales out and looking well.

Princess Kate mentioned in her Sept. 9 announcement about completing chemo that she was "looking forward to being back at work and undertaking a few more public engagements in the coming months when I can." It emerged than that the royal hoped to join her family at the Cenotaph Service on Remembrance Sunday, a event she has never missed since marrying William in 2011. 

"Being a senior member of the royal family and doing these ceremonial events is obviously important to her," says Bedell Smith, author of Elizabeth the Queen.

Next up for the Princess of Wales is her annual Christmas carol concert, which PEOPLE confirms will be in December.