Prince William provided a candid glimpse into what it was like to cope with the death of his mother as a teenager when he visited a child bereavement centre in East London this week.

The Duke of Cambridge was just 15 years old when his mother, Diana, died in a car crash in a Paris tunnel in August 1997. His younger brother, Prince Harry, was just 12.

The immense loss was on William’s mind Tuesday, when he made an official visit to a centre run by Child Bereavement UK, a charity that supports families and children facing bereavement.

Joined by his wife Catherine, the Duchess of Cambridge, William marked the first anniversary of the opening of the charity’s centre in Stratford, U.K. At the centre, Prince William spoke with grieving children, including nine-year-old Aoife, who lost her father to cancer.

“Do you know what happened to me? You know I lost my mummy when I was very young too,” William was quoted as saying. “I was 15 and my brother was 12. So we lost our mummy when we were young as well. Do you speak about daddy? It’s very important to talk about it, very, very important.”

Shinobi Irons, a 12-year-old boy who lost his grandmother and godmother, also chatted with the Duke. Irons’ mother told a U.K. publication that the Duke told her son that he was “very angry” when his mother died, 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,” the mother added. “It was very personal and it was very special.”

The Duke of Cambridge has been a royal patron of Child Bereavement UK since 2009.

In a statement, Ann Chalmers, chief executive of the Child Bereavement UK said that the Duke takes a “keen interest in our work supporting bereaved families and training the many professionals whose work brings them into contact with grieving children, young people and parents, helping them to better understand and meet the needs of the grieving families.”

She added that Prince William’s involvement has made a “huge, positive difference” to the charity.

Next August will mark 20 years since Diana’s death followed a car crash in a Paris road tunnel.