The Duke of Cambridge comforted a nine-year-old girl who had lost her father, and told her how important it is to talk about her grief.
During a visit to an east London bereavement centre with the Duchess of Cambridge, the prince asked Aoife: "Do you know what happened to me?
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Duke and Duchess of Cambridge visit childrens charity
During a visit to an east London bereavement centre with the Duchess of Cambridge, the prince asked Aoife: "Do you know what happened to me?"
"You know I lost my mummy when I was very young too. I was 15 and my brother was 12. So we lost our mummy when we were young as well.
"Do you speak about your daddy? It's very important to talk about it, very, very important."
Aoife's mother, Marie, said afterwards: "I couldn't believe it when he started to talk about his mother. It was very emotional and I was willing myself not to start to cry. I almost did.
"I am telling my children that if they take anything away from this day, it is what he said about how important it is to talk. Kids do not forget that. Sometimes it hurts but we can remember the happy things too. It is so important to talk."
The prince also made a rare public admission about his feelings following the death of Diana, Princess of Wales, telling a grieving boy he was "very angry" when his mother died.
William's candid comment came at the start of a year that will see the 20th anniversary of Diana's death marked over the coming months.
As Lorna Ireland, 36, and her son Shinobi Irons, 12, each filled their individual jars with bands of coloured salt - representing memories of the youngster's grandmother who died three years ago and godmother who died in 2015 - the future king spoke about his feelings.
Miss Ireland said: "He told my son that when his mum died he was 15 at the time and he was very angry and found it very difficult to talk about it.
"So it was very important that Shinobi talked to somebody about how he was feeling even now years on."
She said about the admission: "It was very personal and it was very special."
The Duke was a teenager and his brother Prince Harry was just 12 when their mother Diana was killed in a car crash in Paris on August 31 1997.
In recent years the royal siblings have begun to talk about their feelings surrounding their loss with Harry saying last summer in an interview he now regrets not opening up sooner about how his mother's death affected him.
William and Kate were visiting a bereavement centre in Stratford run by Child Bereavement UK which the Duke supports as royal patron.
The organisation, first launched in 1994, had Diana as a keen supporter and today it continues to support parents who have lost children as well as offering help to a child if they experience bereavement themselves.
The Telegraph, London