The British royal teared up as he referenced Princess Diana while delivering a poignant speech in Manchester.
Prince William was speaking at the official opening of a memorial at the Manchester Arena for the 22 victims who died there in 2017 during a bombing which took place during an Ariana Grande concert.
The memorial, titled Glade of Light, is a giant white marble halo featuring the victims' names.
During the ceremony, William explained why he and his wife felt they had to attend the event, which took place just before the fifth anniversary of the bombing.
“For Catherine and I, it is very important that we are with you here today. To remember the 22 lives so brutally taken,” William said. “To acknowledge the hundreds of lives that were irrevocably changed and to pay tribute to the resilience of this great city.”
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The 39-year-old future king went on to recall his visit to Manchester just days after the incident, which left hundreds injured.
"I remember only too well the shock and grief on the faces of those I met when I visited Manchester in the days following the atrocity,” the prince said.
“And the rawness of emotion at the commemoration service, held at your cathedral just here, a year later.
“Five years on, I know that the pain and the trauma felt by many hasn't gone away.”
The prince then became emotional when he referred to losing his mother, Princess Diana, in 1997.
“As someone who lives with his own grief, I also know that what often matters most to the bereaved is that those we've lost aren't forgotten.
“There's comfort in remembering. In acknowledging that, while taken horribly soon, they lived. They changed our lives,” said the prince, who was 15 years old at the time of Diana’s death.
“They were loved. It's why memorials such as the Glade of Light are so important, why Catherine and I so wanted to be amongst you today.”
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The father of three ended off his speech by urging everyone to keep the victims' families in their hearts and prayers.
“On that day you told each other that you wouldn't look back in anger. And you showed the world the true heart of this extraordinary place,” William said. “So, when we come to this memorial, let’s look back with love for those we lost.”
After William’s touching speech, Figen Murray, whose son Martyn Hett (29) died in the bombing, told the Manchester Evening News how touching the royal's speech was.
“The two of them [William and Kate] coming was very special,” Figen said. “William has his own experience of grief and you could tell all the words he said came from the heart.
“Their words were beautiful and they took so much time to speak to all the families here today.”
William also spoke of his grief last year at the opening ceremony of the General Assembly of the Church of Scotland last year, he detailed his “dark days of grief” following her fatal car crash in Paris in 1997.
“I was in Balmoral when I was told that my mother had died. Still in shock, I found sanctuary in the service at Crathie Kirk that very morning,” William said.
“And in the dark days of grief that followed, I found comfort and solace in the Scottish outdoors.
“As a result, the connection I feel to Scotland will forever run deep. And yet alongside this painful memory, it is one of great joy.”
Sources: DAILY MAIL, MANCHESTER EVENING NEWS, US WEEKLY, PEOPLE, TOWN AND COUNTRY